The evolution of the expansion of a supernova remnant, detailed monitor- ings of gamma ray bursts, studies of the storms in Saturn and Jupiter, the first brown dwarf, the confirmation of the presence of black holes in bina- ry stars, models for novae and supernovae, the role of magnetic fields in the rotation pattern of galaxies, sunspots phenomena, the methane cycle in Titan, the impacts of volatile material on the Moon, the discovery of a spherical bubble around a stellar embryo, the description of the inter- galactic medium...
These are some of the results we present in ‘Astronomy made in Spain’, a project of the Spanish Astronomical Society (Sociedad Española de Astronomía, SEA) to commemorate the International Year of Astronomy 2009. This book is a collection of conversations with the Spanish astronomers who have published as first authors a paper —at least— in Nature or Science in the last 30 years. We would like this legacy paid homage to all Spanish astronomers, stimulated the new generations of students and composed a living history of discoveries told at first hand, without any intermediaries, by the people who made them possible.
Benjamín Montesinos Emilio J. Alfaro
First English Edition, 2011 © First and second Spanish editions, Sociedad Española de Astronomía (SEA) 2009, 2010 © First English edition, Sociedad Española de Astronomía (SEA), 2010 Facultad de Física Universidad de Barcelona Av. Martí Franquès, 1 08028 Barcelona Spain e-mail: [email protected] http://www.sea-astronomia.es
© Translation: Susana Cabañero Rodríguez © Copyeditting of the translated text: Aprajita Verma © Illustrations: Pages 16, 32, 40, 48, 64, 90, 94, 104, 114, 122, 126 and 130: NASA, ESA, The Hubble Heritage Team (STScI/AURA) Pages 24 and 134: NASA/JPL/University of Arizona Page 52: Royal Academy of Sciences, Sweden Pages 56 and 108: TRACE Project and NASA Page 78: SOHO/EIT (ESA, NASA) Page 86: NASA/CXC/SAO/S. Murray, M. Garcia Page 118: Lawrence Berkeley National Laboratory Page 142: ESA/Consortia LFI and HFI Page 146: Apollo VIII (NASA)
Publisher: Sociedad Española de Astronomía (SEA) Design and production: Cyan, Proyectos Editoriales, S.A., Madrid
The contents of each chapter are a property of the corresponding researcher. No reproduction of any part of this book may take place without the written permission of the author, which can be obtained through the Sociedad Española de Astronomía. Index of authors
Preface ...... 7 Jordi Isern Vilaboy ...... 9 Enrique García-Berro Montilla...... 11 David Valls Gabaud...... 17 Xavier Barcons Jáuregui ...... 21 Agustín Sánchez Lavega ...... 25 Jorge Casares Velázquez...... 29 Eduardo Battaner López...... 33 Evencio Mediavilla Gradolph ...... 35 Juan María Marcaide Osoro ...... 37 Vicent Martínez García...... 41 Francisco J. Castander Serentill...... 45 Rafael Rebolo López...... 49 Carlos Westendorp Plaza ...... 53 Benjamín Montesinos Comino...... 57 Ramón Oliver Herrero ...... 61 José Cernicharo Quintanilla...... 65 Eduardo Martín Guerrero de Escalante...... 69 Alberto J. Castro Tirado...... 71 Pere Planesas Bigas ...... 75 Héctor Socas Navarro...... 79 Vicent Quilis Quilis...... 83 Josep María Paredes Poy...... 87 José Luis Ortiz Moreno ...... 91 José Luis Gómez Fernández ...... 95 María Rosa Zapatero Osorio ...... 97 Garik Israelian ...... 99 José María Torrelles Arnedo...... 101 Luis Felipe Miranda Palacios ...... 105 Javier Trujillo Bueno ...... 109 Margarita Hernanz Carbó ...... 115 Jordi Miralda Escudé ...... 119 Josep Miquel Girart Medina...... 123 Aníbal García Hernández ...... 127 María Teresa Beltrán Sorolla ...... 131 Ricardo Hueso Alonso ...... 135 Rafael A. García Bustinduy ...... 139 Marcos Cruz Rodríguez...... 143 Enric Pallé Bago...... 147 María de Santos Lleó...... 151 Preface
This is the English edition of the book “Astronomía made We present here 39 conversations with the Spanish in Spain”, an idea that materialized in 2009, the astronomers who have published as first authors in Nature International Year of Astronomy. In order to celebrate and Science in the last 30 years, until the end of 2009. The that event, the Spanish Astronomical Society (Sociedad same questionnaire was sent to each researcher. They were Española de Astronomía, SEA) had the idea of publishing asked to describe in the simplest possible way the context a book summarising the history of modern Spanish and scope of their discoveries and also to provide some Astronomy through the personal views of the researches personal appreciations or anecdotes. When an astronomer themselves through their discoveries. Papers published in had more than one publication, he or she was asked to Nature and Science were chosen as samples of the work that choose one, or to summarise the results of several or all has propelled Astronomy in Spain to the healthy stage we of them. At the end of each conversation you will find enjoy today. Those two publications were awarded the the reference of the paper (or papers) treated in the text. 2007 Prince of Asturias Prize for Communication and We have placed the contributions in chronological order Humanities. As it was expressed in the resolution of the according to the publication date of the papers, to give committee: “…both journals represent the most reliable a general perspective of the way the different branches have channel of communication that the international scientific evolved. community has today for reporting, after a meticulous and impeccable selection process, the most significant research You will find very different styles of writing, long texts and discoveries in very diverse scientific fields, and at the in some cases and more laconic ones in other occasions, same time, disseminate the most elevated theories and as well as different complexity levels when describing the facts, whilst combining rigour and clarity. Science and scientific topics. Corrections and editting of the original Nature are indispensable sources of information for texts have been kept to a minimum. The editors are specialized journalism in every country. For over a century, indebted to Susana Cabañero for a very careful translation they have promoted and disseminated mankind’s great of the originals in Spanish and to Aprajita Verma for scientific conquests and thus have brought science closer revisions and copyeditting of the translated texts. Each to life.” contribution was sent to the corresponding author who
7 made the final “fine tuning” of its contents. We are also once made a milestone discovery in their fields describe grateful to Montserrat Villar, the coordinator of the 2009 their experience at first hand. International Year of Astronomy Spanish Node, for providing us with finantial support for the translation. Benjamín Montesinos Comino It is always stimulating to read about a historical event Emilio J. Alfaro Navarro, when described by a person who was there. It is the same on behalf of the Spanish Astronomical Society (SEA) in science. There is nothing better than letting people who February 2011
8 Jordi Isern Vilaboy Institut de Ciències de l’Espai (CSIC-IEEC, Barcelona)
What was the problem you had outbursts and neutron stars in low-mass which have culminated with the to face? X-ray sources could have the same origin, discovery, thanks to Type Ia Type Ia supernova outbursts are the namely, a carbon-oxygen white dwarf. supernovae, of the accelerated result of the thermonuclear explosion The difference in behaviour was due expansion of the Universe, but the in a white dwarf in a close binary star to the value of the central density at problem of the residual intrinsic system. These outbursts are the moment of ignition and to the dispersion in the luminosity of Type characterised by a very homogeneous changes in chemical composition Ia supernovae at maximum still remains. maximum luminosity and the induced by solidification. If the density correlation between the existing was very high (which is the case of Which are the main problems luminosity dispersion and the light initially cold stars), the electronic in this area of Astrophysics and curve decline rates. In 1984, it was not captures on the ashes could trigger the what are the expected discoveries yet clear if the nature of these outbursts collapse to a neutron star, while the in the coming years? was thermonuclear or gravitational and differences in the chemical The problem mentioned before is part the cause of the above mentioned composition could change the of a more general problem concerning correlation (known as the “Phillips propagation velocity of the deflagration the behaviour of degenerate stellar Relation”) was unknown. and explain the small luminosity structures that are responsible for a dispersion at maximum. large number of astrophysical What was the solution to this problem phenomena. The rich and precise and the contribution this paper made Since the paper was published, have astrophysical data we are obtaining to the area of expertise in which it is there been significant advances currently, and those that will be framed? in this specific area? provided by future telescopes, will In this paper we proposed for the first There have been important advances allow us to use the stars as large time that thermonuclear supernova from the observational point of view physics laboratories. 9 Astronomy made in Spain
How did it influence your moment, the existence of monopoles, professional career? Have you or the compactification of extra continued in that line of work? Has dimensions. it opened new perspectives or later did you dedicate yourself to other Do you have any anecdote related topics? to this paper’s gestation and The physics of stellar interiors has publication that you think is worth been fundamental in my professional telling? career. It determines not only the The idea of writing this paper came Figure 1. Type Ia supernova progenitor model. behaviour of the late evolutionary up during a meal at “Motel Matter from its companion falls onto the surface phases of stars (supernovae and white Empordà”, in Figueres (Alt of the white dwarf causing the inner regions to dwarfs) but also properties of the Empordà), while we were enjoying become unstable and producing a thermonuclear Galaxy (nucleosynthesis and chemical a roast deer (solid phase) in quince explosion. Image by Paul Ricker, University of Illinois. evolution, fossil stellar populations, jelly (liquid phase). etc.). The simplicity of white dwarfs and the paradigm of these degenerate structures, allow us, using them, to SOLID WHITE DWARFS AS TYPE I SUPERNOVA define “exotic” physics theories as PROGENITORS gravitational constant drifts, axions J. ISERN, J. LABAY AND R. CANAL mass, the neutrino magnetic 1984, NATURE, 309, 431
10 Enrique García-Berro Montilla Departamento de Física Aplicada Universidad Politécnica de Cataluña (Barcelona)
What was the problem you had second half of this decade Dense plasma physics predicted that to face? observational data of better quality the material of the degenerate core The evolution of white dwarfs was were obtained in a systematic and of the white dwarf, composed of a problem that gave rise to an routinely way for a limited number carbon and oxygen nuclei, should important debate in the eighties. It of this type of stars. In particular, experience a first-order phase has been known for some time that precise distances could be obtained transition at sufficiently low the evolution of white dwarfs was for about 200 white dwarfs, which temperatures or, in other words, that driven by two important factors. allowed the number of white dwarfs the white dwarf’s interior should Firstly, it was known that the per unit bolometric magnitude crystallize, with those nuclei pressure of a gas of degenerate and per unit volume to be measured, forming a crystalline lattice. As a electrons supports the mechanical i.e. the luminosity function of white result, an additional energy should structure of white dwarfs. The dwarfs. It was then purely a matter be released, the latent heat of second fact that was known is that of comparing the theoretical crystallization. Some previous a simple cooling process could models of white dwarf cooling with studies also showed that it was describe the evolution of this type the derived luminosity function. The possible that the chemical of star. Both facts were fully results of this comparison were composition of the solid phase was established and widely accepted shown in the paper I published different to that of the liquid one. by the astronomical community. in Nature. In particular, some theoretical However, we had very few good calculations showed that the solid quality observations of white dwarfs, What was the solution to this phase should be richer in oxygen. As which made the comparison between problem and the contribution this a result of this and the high gravity the theoretical models and the paper made to the area of expertise of white dwarfs, the central regions of observations very difficult. In the in which it is framed? the white dwarf would be oxygen-rich, 11 Astronomy made in Spain
as the crystallized material is denser the Galaxy. This simple reasoning models allowed us to determine than the liquid, which would be can be refined using the luminosity the age of the Galaxy. carbon-rich. The separation of function (a statistical measurement). carbon and oxygen releases It is well known that the colder an Since the paper was published, additional energy which should object is, the longer it takes to cool have there been significant be radiated by the white dwarf, down. In the case of white dwarfs, advances in this specific area? therefore altering its cooling rate. this means that the fainter a white There have been enormous advances This is due to the fact that the dwarf is, the longer it takes to in this area of astronomy. Today, all material has to be electrically decrease its intrinsic brightness. theoretical models of white dwarf neutral, and therefore, the oxygen- The probability of detecting a white cooling include the phase separation rich solid material carries with it dwarf with a specific luminosity of oxygen and carbon. Besides, as additional electrons, therefore depends mainly on how long it a result of systematic sky coverage modifying the pressure balance. maintains that luminosity. (2MASS, SDSS, 2dF…) the number Our detailed calculations took into Therefore, the white dwarf of white dwarfs accessible to high- account the resulting energetic luminosity function should be a quality observations has increased balance and allowed us to obtain monotonically increasing function outstandingly, going from about 200 the cooling rate of white dwarfs for decreasing luminosities, as low- white dwarfs to more than 6,000. with high precision. luminosity white dwarfs take longer This has permitted the construction On the other hand, it was already to cool. The first observational of very precise luminosity functions known before our work that white determinations of the luminosity which allow conclusions about the dwarfs could be used as stellar function confirm this hypothesis. physical processes that take place in chronometers. It was speculated that The surprise was that the the interior of white dwarfs to be as the evolution of white dwarfs determinations of the luminosity drawn. In particular, about exotic could be considered as a cooling function, which were published particle emission, like the axion. It process, and given the very narrow during those years, presented a very is also possible to obtain statistical mass distribution of white dwarfs, if sharp decrease at low luminosities, limits on a hypothesised variation we detected the faintest white dwarf indicating a substantial deficit of of the universal gravitational in the solar neighbourhood we these low-luminosity stars. This constant predicted by some would be looking at the oldest one decrease in the number of white alternative gravitational theories, and, therefore, knowing its age, we dwarfs was quickly attributed to the but which still need to be confirmed. could put a lower limit to the age of finite age of the Galaxy and our In the near future, ESA’s Gaia 12 Spanish Astronomical Society
astrometric satellite will help us to and halo). Also, the observations astrophysics which have nothing extend the observational data base from space platforms will make it to do with the evolution of white even more with which it will be possible to obtain very high quality dwarfs. Regarding the question possible to precisely measure the data, both from field white dwarfs about the influence of this paper on stellar formation rate in the solar and white dwarfs in clusters, either my professional career, I have to say neighbourhood using the white in open or globular clusters. The that when I published this paper dwarf luminosity function, among perspectives in this sense are very I did not give it the importance I other potential applications. For all wide as it will be possible should have. With time I have this, it will be necessary to improve to compare several methods to developed a different perspective. the models of white dwarf cooling. determine the age of clusters. It should be taken into account that Future perspectives opening up in Therefore, the theoretical models when I published this paper I was this field are therefore very of the evolutionary properties of in the last stage of my PhD thesis. promising. white dwarfs is showing notable Now, I value the contribution advances. the paper made as it deserves Which are the main problems in to be. this area of Astrophysics and what How did it influence your are the expected discoveries in the professional career? Have you Do you have any anecdote coming years? continued in that line of work? related to this paper’s gestation One of my fields of work is still Has it opened new perspectives and publication that you think the evolution of white dwarfs. The or later did you dedicate yourself is worth telling? determination of their observational to other topics? Nothing in particular, simply properties and physical Yes. The answer to both questions the great moments I had with the characteristics are still today very is positive. I have maintained an co-authors of the paper. The active research fields. In the next active line of research in the field calculations were done with very few years, important advances are of white dwarfs, which has been different resources to the ones expected, especially in relation to extended to other related areas. available today and, to a large extent, the pulsational properties of white I have dedicated most of my time to they were the result of scientific dwarfs. Some significant advances this research field, as I feel very discussions and the co-operation are also expected in the comfortable with it and find it very and friendship among the authors. determination of different interesting. Of course, I have also Co-operation and friendship that populations of white dwarfs (disk worked in other aspects of still exist today. 13 Astronomy made in Spain
ADDENDUM: …23 years later NGC 6791 is an open cluster close to the Sun and very well studied. It has been possible to obtain images of its stars reaching very faint magnitudes, even fainter than those corresponding to the end of the cooling sequence for white dwarfs. In addition, it is a very populated cluster, old and metal rich. It was already known that there was a remarkable discrepancy between the age of the cluster obtained by fitting the main sequence (8 x 109 years) and the one estimated from white dwarfs (6 x 109 years), but there was no plausible hypothesis to account for that difference. An explanation is that, given the high metal abundance of this cluster, one of the products of Helium burning, namely 22He, settles towards the interior of its white Figure 1. Image of the globular cluster NGC 6397. The image on the left corresponds to the field observed by dwarfs, releasing gravitational energy. the Hubble Space Telescope. The faintest stars in this field are red dwarfs and white dwarfs. The first ones In addition, as we suggested back in have a magnitude of 26, while the latter have a magnitude of 28. The image at bottom right shows the 1988, at even lower temperatures, the faintest red dwarf (inside the circle). The image at top right shows one of the faint white dwarfs in the field, main components of a typical white the blue star surrounded by a circle. Note the different colours of the stars. dwarf (12C and 16O) crystalize, producing their separation in solid phase, releasing more energy and delaying the cooling of the white dwarf. In our paper published in Nature in 2010 (see the reference 14 Spanish Astronomical Society
below) we demonstrate that taking into account the delays induced by PROPERTIES OF HIGH-DENSITY BINARY MIXTURES AND both phenomena, the ages -obtained THE AGE OF THE UNIVERSE FROM WHITE DWARF STARS using the methods mentioned above- E. GARCÍA-BERRO, M. HERNANZ, J. ISERN AND R. match each other. In this way we have MOCHKOVITCH proved that the mechanism we 1988, NATURE, 333, 642 suggested 23 years ago does actually occur in the dense nuclei of white A WHITE DWARF COOLING AGE OF 8 GYR FOR NGC dwarfs. It was a great pleasure to see 6791 FROM PHYSICAL SEPARATION PROCESSES that what we proposed was finally E. GARCÍA-BERRO, S. TORRES, L.G. ALTHAUS, I. confirmed by observations. In RENEDO, P. LORÉN-AGUILAR, A.H. CÓRSICO, R.D. opposition to my feelings in 1988, ROHRMANN, M. SALARIS AND J. ISERN in this case I valued a lot to see our 2010, NATURE, 465, 194 paper published… No doubt, I accumulate 23 more years of experience…
15
David Valls Gabaud CNRS, Observatoire de Paris (Francia)
What was the problem you had formation theory is that the initial filaments that characterise the large- to face? galaxies, less massive and therefore scale structure of the Universe. This The second half of the 1980s marked less biased with respect to the mean distribution was roughly the one a milestone in the galaxy formation value, should have a very different predicted by this galaxy formation scene. For the first time, a very spatial distribution to that of the theory, so it was essential that the detailed theoretical picture was being brightest and more massive galaxies, theory undergo a more detailed developed based on just one much more biased. The object of testing. Due to the small number hypothesis. It was postulated that the test was, therefore, to measure of galaxies available (barely more dark matter, which forms haloes the spatial distribution of the than a thousand, but they surrounding the observed galaxies, brightest galaxies with respect revolutionised cosmology) it was very would have a low thermal velocity to the faintest galaxies. difficult to measure these subtle (Cold Dark Matter or CDM) in effects. The first step was to develop opposition to the alternative What was the solution to this a new robust statistical method that hypothesis according to which dark problem and the contribution enabled the theory to be tested with matter consisted of lighter this paper made to the area of a relative measurement of the effect elementary particles, such as expertise in which it is framed? instead of trying to measure the neutrinos. Within this framework, it It was hard to prove this prediction effect in an absolute way. can be shown that dark matter haloes with even the most detailed galaxy The measurements made in the form in a hierarchical way: The less catalogues of the time. This situation CfA catalogue delivered amazing massive haloes collapse first and start changed with the galaxy catalogue results, and so the second step was merging with others, forming made by a Harvard CfA team to analytically calculate the detailed increasingly larger halos. One of (Huchra, Geller and De Lapparent), predictions that were feasible within the predictions of this biased galaxy which showed for the first time the the framework of the galaxy 17 Astronomy made in Spain
L/L*
0,02 0,05 0,1 0,2 0,5 1 25
CfA VGAB (1989)
2 dF (2002) early 2dF (2002) late 2dF (2002) all
SDSS (2002) all ) * CDM [old simulations] b(M) / b(M
0,5 1-16 1,5 -17 2 -18 2,5 -19 3 -20 -21 M 5 log h
Figure 1. Variation of the relative bias parameter of galaxies as a function of luminosity (left) and absolute magnitude (bottom). In red, the measurements from the CfA catalogue in 1989. The dashed and continuous lines represent several analytic models of galaxy formation in the CDM paradigm. The crosses and circles are the predictions of numerical simulations with CDM at that time, which were clearly in contradiction with observations. The most recent measurements with much deeper catalogues are shown in green (2dF catalogue) and blue (SDSS catalogue). The present measurements show that the issue is not yet settled. The bias of bright galaxies in the 2dF catalogue is very different from the one in the SDSS catalogue, and some dwarf galaxies seem to have a large bias in the 2dF catalogue but not in the SDSS. The local density of galaxies probably determines the bias, as well as the luminosity of galaxies or the mass of dark matter haloes. 18 Spanish Astronomical Society
formation theory. The result was that of observation at the Very Large baryonic acoustic oscillations, which the measurements were clearly in Telescope (VLT, ESO, Chile). New are a reflection of what happened contradiction to both the refined catalogues, with nearly a million when the Universe became analytical predictions and the first galaxies, have yielded contradictory transparent to photons and at numerical simulations of large results (Figure 1) both between a regime where the bias is supposed structures. Theory could not explain, themselves and in comparison to to be known and simple. Yet the in a simple way, the large-scale theory. Now we think that the measures can be affected by the distribution of brightest galaxies luminosity of galaxies is not uniquely luminosity dependence of galaxy compared to the faintest galaxies, determined by the mass of the dark bias, as we have just seen, and these and therefore, it was not possible matter haloes surrounding them, but effects may skew the measurements to understand how galaxies actually there are more subtle effects that can of the cosmological parameters. formed. have an influence, such as the local There is still plenty of work to do density of galaxies. For example, the with present catalogues in order to Since the paper was published, have galaxies in clusters are in denser understand in detail the there been significant advances environments, and this can influence characteristics of large-scale galaxy in this specific area? their star formation histories which, distribution and, therefore, to Yes, as we are living what it is in turn, determine the observed understand how galaxies form. probably the golden age of luminosities. Cosmology. On the one hand, the How did it influence your theoretical predictions have advanced What are the main problems professional career? Have you significantly, partly thanks to large- in this area of Astrophysics and continued in that line of work? Has scale numerical simulations. On the what are the expected discoveries it opened new perspectives or later other hand, the spectrographs in the coming years? did you dedicate yourself to other mounted on large telescopes have This field of Astronomy continues to topics? enabled more and more detailed and be very active, especially because it is Publishing a paper in Nature during complete catalogues to be made. Just necessary to understand in detail the your thesis is quite exceptional and to emphasise the order of magnitude, large-scale distribution of galaxies in I was simply lucky to be working what took several years of painstaking order to measure the cosmological in a hot topic with unique tools observations for the CfA team to parameters that describe the Universe (advanced statistical methods, obtain a thousand galaxy spectra, as a whole. For instance, there are analytical calculations in Gaussian now can be done in less than an hour several projects aimed at measuring random fields) when the first “big” 19 Astronomy made in Spain
galaxy catalogue was published. The and the evolution of star formation for a third independent referee who eagerness to work with that catalogue within them. had access to all the correspondence. was so strong that some colleagues He turned out to be none other than even scanned the enlarged Do you have any anecdote related to P.J.E. Peebles, who is widely regarded photocopies of the published figures this paper’s gestation and to be one of the founders of modern because the real catalogue would be publication that you think is worth cosmology, and who sent a highly published much later. telling? favourable report while he criticised The paper, of course, was very This was the second paper I wrote the second referee. I still keep as a useful to obtain my first postdoctoral during my PhD thesis and my first memento the letter that J. Maddox, contract, but I did not continue one published in Nature. I was not the mythic editor of Nature, sent working on that topic until a couple very familiar with the reports sent by accepting our paper, apologising for of years ago when I wanted to referees and it was surprising to the behaviour of the second referee measure the effect in new catalogues, receive one very enthusiastic report and guaranteeing us that this person with results which are surprisingly and another demolishing one. The would never be contacted again by more difficult to interpret. I am second referee took a long time to Nature to referee a paper. taking up this line of work again answer and kept sending more and because of the growing importance of more complicated questions that this field for the future measurements could not be resolved in the LUMINOSITY SEGREGATION AS A CONSTRAINT ON THE of cosmological parameters and also framework of a short Letter to Nature THEORY OF BIASED GALAXY FORMATION to understand the mechanisms that and which were not related to the D. VALLS-GABAUD, J.-M. ALIMI AND A. BLANCHARD determine the luminosity of galaxies topic. In the end, we decided to ask 1989, NATURE, 341, 215
20 Xavier Barcons Jáuregui Instituto de Física de Cantabria (CSIC-UC, Santander)
What was the problem you had background light (especially microwaves and, for the time being, they are largely to face? and X-rays) present in the Universe. theoretical. Hydrodynamical Our aim was to try to understand the We reached the conclusion that the simulations made in the current physical state (temperature, density, present temperature of the intergalactic cosmological paradigm show that, homogeneity) of atoms and ions that medium would be between 20,000 indeed, half of the atoms in the are thought to be dispersed in between degrees and about 10 million degrees. Universe are in a diffuse phase in the galaxies. It is not expected that 100% This temperature interval was intergalactic medium. They also show of atoms are captured inside galaxies inconsistent with the idea of that the temperature of this diffuse or galaxy clusters during the galaxy attributing the origin of energetic medium was several hundred thousand formation process thereby predicting X-rays (the cosmic X-ray background), degrees when the Universe was one the presence of atoms and ions in the that fill the Universe, to the third of its present age, but today it intergalactic medium. intergalactic medium, a model we had could have a temperature of many defended previously. It also rejected million degrees. Finally, the simulations What was the solution to this one of the cosmic structure formation show that the intergalactic medium problem and the contribution models at that time, based in big is likely to be distributed in the form this paper made to the area of cosmic explosions, which other of filaments, similarly to dark matter. expertise in which it is framed? researchers were putting forward. We used three cosmological observables Which are the main problems to infer the density and temperature of Since the paper was published, have in this area of Astrophysics and the intergalactic medium. The first one there been significant advances what are the expected discoveries derives from distant quasar observations, in this specific area? in the coming years? the second and third ones from the The most significant advances have There is a possibility that the observation of all types of extragalactic been achieved during the past decade current generation of X-ray space 21 Astronomy made in Spain
Figure 1. The figure shows a numerical simulation of how matter is distributed in the integalactic medium in the current universe. The regions with larger densities mark the position of galaxies and clusters of galaxies, but the majority of that medium is too diluted to be seen with the current astronomical instrumentation. An interesting point is that, instead of being uniformly distributed, the intergalactic medium shows a filamentary structure. In that way, if a beam of light from a distant object crossed one of those filaments, the next-generation X-ray telescopes would be able to see the trace of that filament in the light of that far-away source. Figure taken from R. Davé et al. 2001, The Astrophysical Journal, 552, 473.
observatories detect the first traces sources, such as quasars or very its temperature, but for the time (or filaments) of the hot luminous similar objects. With the being there is no clear conclusion. intergalactic medium (temperatures aid of Chandra and XMM-Newton In the best case, these missions of million degrees), through the missions, we have been searching for would enable us to find only the fingerprint that highly ionized these “absorption lines” of six-times- very first intergalactic medium oxygen atoms would leave in the ionized-oxygen that is the state in filaments. However, their study will X-ray light we receive from distant which it would preferably be, given have to await until the launch of the 22 Spanish Astronomical Society
International X-ray Observatory capability as that of IXO was what external referees were assigned, one (IXO) towards 2020. was exactly needed to tackle this from each of these communities. problem. Each of them, who had no strong How did it influence your professional argument against the paper, career? Have you continued in that Do you have any anecdote related pretended that the paper had to line of work? Has it opened new to this paper’s gestation and derive its emphasis towards the field perspectives or later did you dedicate publication that you think is worth of the other one: It seemed that they yourself to other topics? telling? did not want intruders. The editor For more than a decade I stopped my What I am going to tell it is related had to intervene and decided to research on this topic. From 1997 to a different paper I published in accept the paper. Several years later, onwards, I became interested again Nature with other colleagues one of those referees confessed to me when I got involved in the scientific (Extensive dark-matter haloes in low- that he was one of them (we had definition of the IXO mission luminosity galaxies revealed by quasar already identified the other one) (formerly know as XEUS) following absorption-lines, X. Barcons, K.M. and he recognized his behaviour with a collaboration among the European Lanzetta, J.K. Webb, 1995, Nature that paper was perhaps not the most Space Agency (ESA), the U.S. Space 376, 321). This paper mixed two constructive one. Agency (NASA) and the Japanese aspects of the study of galaxies that, Space Agency (JAXA). Together with at least at that time, were regarded as other colleagues we saw that the very different: QSO absorption lines THE PHYSICAL STATE OF THE INTERGALACTIC MEDIUM combination of a large effective area caused by neutral gas along the line X. BARCONS, A.C. FABIAN AND M.J. REES together with a spectral resolution of sight and galaxy kinematics. Two 1991, NATURE, 350, 685
23
Agustín Sánchez Lavega Departamento de Física Aplicada I Escuela Técnica Superior de Ingeniería Universidad del País Vasco, Bilbao
What was the problem you had created for the first time a dynamical multicolour images of the early phases to face? model of the nature of the spots. of the storm and its development When I was 16, I was able to look And, as they are apparently recurrent and evolution for more than a year. at the Universe for the first time with a with Saturn year (30 terrestrial years), We could measure in detail the storm small telescope that I bought with we raised the possibility that a new clouds movements and the planet’s the pocket money I managed to save, storm would be visible in 1990. equatorial winds. With all these data, and since then this was always the It indeed happened, and it was the and with those obtained later with the only thing that strongly caught my study of this phenomenon that Hubble Space Telescope (HST), which attention. What were those bright brought us for the first time to the had been recently launched at the time, and dark spots that could be seen front page of Nature. we were able to put a limit to the over the trembling disks of Mars and height of clouds and improve the Jupiter? These and other questions What was the solution to this dynamical model of the storm. We lead me to study the planets, and, in problem and the contribution could determine that the giant storm particular, to explore the atmospheres this paper made to the area of was caused by convection in deep water of the giants Jupiter and Saturn. For expertise in which it is framed? clouds in Saturn’s atmosphere. my PhD thesis I studied the winds of Saturn’s equatorial storm appeared at Saturn and especially, the strange and the end of September 1990 and it was Since the paper was published, have giant storms (“Great White Spots”), discovered by a North American there been significant advances rummaging in libraries to collect the amateur astronomer. A few days later, in this specific area? scarce data available. There were only we could observe it in detail with the The work published in Nature was four documented events after more 1 meter telescope at the Pic du Midi later the basis of two PhD theses in that 120 years of observation, and Observatory in the French Pyrenees. our research group (and some others with the information we gathered we We collected an excellent set of in the United States). The published 25 Astronomy made in Spain
work enabled an advance in the details planets is to know the nature of the formation of these storms and of its multiple and intense winds in the structure of the planet’s the form of jet streams which vary atmosphere. It also happened that with latitude. We do not know if a new second storm came up in the they are deep and extend down into equator in 1994, and we published the interior of Jupiter and Saturn, another work in Science about it. A or if they are a superficial Figure 1. Images of Saturn’s equatorial storm paper we wrote some years later in phenomenon and, therefore whether obtained in October 1990 from the Pic du Midi 2003, again occupied the front page of the source of energy is the Observatory. The letters on the images correspond to Nature, where based on the analysis deposition of solar radiation the names given to the different colour filters used. of HST images we suggested that the (which arrives from the top) or the apparent change in velocity of Saturn’s internal energy retained inside strong equatorial jet stream could be the planet after its formation (which the result of giant storms. Since then flows from beneath). At the there has been a great advance in the beginning of 2008, we got our third knowledge of this planet and, in front page of Nature with a work particular, its atmosphere, after the about Jupiter’s intense tropical jet in Cassini spacecraft entered into orbit which we studied the relationship Figure 2. Images of in the middle of 2004. Cassini is between two strange storms (similar Saturn in 1990 (above) allowing us to study Saturn’s wind to the ones in Saturn), the planetary and 1994 (right) system and meteorology. However, disturbance they produced and the showing the storms there have not yet been any great depth of the jet stream where (Great White Spots) at storms while the spacecraft has been they emerged. We think the jet those years. The colour images were obtained in orbit around the planet… stream is deep. Another with the Hubble Space fundamental problem is the Telescope (HST), and the Which are the main problems determination of the water vapour black-and-white image is in this area of Astrophysics and abundance and its spatial and from the Pic du Midi what are the expected discoveries temporal distribution necessary Observatory. in the coming years? to explain the meteorological One of the big problems of phenomena in the atmospheres atmospheric dynamics of giant of these planets. 26 Spanish Astronomical Society
How did it influence your professional Do you have any anecdote related career? Have you continued in that to this paper’s gestation and line of work? Has it opened new publication that you think is worth perspectives or later did you dedicate telling? yourself to other topics? I learnt about the eruption of There is no doubt that publishing in Saturn’s equatorial storm in 1990 Nature and Science, and even more, through a telephone call from the Pic occupying their front pages, is probably du Midi Observatory at 2 in the the best showcase of the research that morning. I was told it was one is carrying out to other scientists in spectacular and that they were the same field and in related areas, and photographing it in detail. The to the mass media. Our group has been following day I took an 8-inch successful in this respect, with six Celestron telescope and I was papers in Nature (three times at the observing it with my younger son front page) and another three in from a cliff near my house when the Science. This has definitely contributed storm, like a bright dot, crossed the to the public image of this research, central meridian of Saturn’s disk. I both among colleagues and socially was profoundly impressed! In the through conferences, papers, following months I was observing interviews, etc. This has given us the with the 1-meter telescope at Pic du foundation to extend our research to Midi in very hard winter conditions the atmosphere’s of other planets, such and sometimes pointing towards as the study of the wind system of Saturn when it was only 20º above Venus using data from the Venus the horizon! In an innocent way, Express spacecraft, and the methane without knowing the consequences storms on Titan. it could have, I sent the paper on the storm to Nature. The referees
received it so enthusiastically Figure 3. Front pages of Nature, which correspond (opinions were exchanged by email, to the papers published by the group at the which it was not a standard yet) that University of the Basque Country about Saturn’s the editor decided to publish it as a storms and Jupiter’s tropical jet 27 Astronomy made in Spain
long Article. I received the acceptance and the proof-sheet in a long fax, and THE GREAT WHITE SPOT AND DISTURBANCES IN the additional surprise arrived when SATURN'S EQUATORIAL ATMOSPHERE DURING 1990 we received the journal in the library A. SÁNCHEZ-LAVEGA, F. COLAS, J. LECACHEUX, P. and saw the storm on the front page. LAQUES, D. PARKER AND I. MIYAZAKI As we did not have enough money to 1991, NATURE, 353, 397 pay the colour copies for the front page, Nature kindly sent me two free LARGE-SCALE STORMS IN SATURN'S ATMOSPHERE copies that I still keep with great DURING 1994 care. That very Thursday, people A. SÁNCHEZ-LAVEGA, J. LECAHEUX, J.M. GÓMEZ, F. from everywhere in the world started COLAS AND 5 CO-AUTHORS to call without stopping to ask about 1996, SCIENCE, 271, 631 the phenomenon. Congratulations from the Spanish Ministry of A STRONG DECREASE IN SATURN'S EQUATORIAL JET AT Education to National Geographic, CLOUD LEVEL from the newspapers to the radio A. SÁNCHEZ-LAVEGA, S. PÉREZ-HOYOS, J.F. ROJAS, R. and the television came flooding in. HUESO AND R.G. FRENCH Without seeking or knowing it, we 2003, NATURE, 423, 623 learnt what it means to publish and occupy the front page of Nature. DEPTH OF A STRONG JOVIAN JET FROM A PLANETARY-
SCALE DISTURBANCE DRIVEN BY STORMS
A. SÁNCHEZ-LAVEGA, G.S. ORTON, R. HUESO, E.
GARCÍA-MELENDO AND 21 CO-AUTHORS
2008, NATURE, 451, 437
28 Jorge Casares Velázquez Instituto de Astrofísica de Canarias (Tenerife)
What was the problem you had was suggested as the “Holy Grail in point in the identification of black to face? the search for black holes” holes. At present, there is no debate In the seventies and eighties three about the existence of black-holes X-ray binaries were identified with What was the solution to this and the word “candidate” has fallen compact objects more massive than problem and the contribution into disuse because all the X-ray 3 solar masses: Cyg X-1, LMC X-3 this paper made to the area sources with dynamic masses over and A0620-00. This value is the of expertise in which it is 3 solar masses are now considered maximum mass allowed for neutron framed? real black holes. stars according to standard models In 1992, using the 4.2 m diameter and, therefore, these binary systems William Herschel Telescope at the Since the paper was published, have would be strong candidates to Observatorio del Roque de Los there been significant advances harbour black holes. However, in Muchachos (La Palma), we managed in this specific area? order to explain the observations, to detect the companion star of the We have moved from having 3 black- some alternative models were X-ray source V404 Cyg and study its hole candidates to 20 confirmed proposed that replace the black hole movement. This star travels faster black holes, 17 in our Milky Way, with two compact stars or new than 208 km/s and completes its 2 in the Magellanic Clouds and one models of “exotic” neutron stars, orbit around a compact object in 6.5 in the galaxy M33. Fifteen of them stable up to 5 solar masses. Then, at days. These numbers imply that it is have relatively precise masses ranging the end of the eighties, there was an more massive than 6 solar masses and between 4 and 15 solar masses. important astrophysical debate about therefore, that would qualify V404 Nobody doubts the existence of black whether black holes exist. In this Cyg as the aforementioned “Holy holes and they are routinely used to context, the detection of a compact Grail” of black holes. One could say explain observed phenomena in a star with a mass over 5 solar masses that our work marked a turning wide range of astrophysical scales, 29 Astronomy made in Spain
Which are the main problems in this area of Astrophysics and what are the expected discoveries in the coming years? In my opinion, there are two fundamental problems in this field: determining the mass spectrum of black holes and the nature of ultraluminous X-ray sources (ULXs). The former has implications in many areas of Astrophysics, such as models for supernova explosions or models of the chemical enrichment of the Galaxy. Unfortunately, our sample of 20 black holes it is too limited to Figure 1. Artist’s concept of the X-ray binary V404 from binary systems to active draw conclusions about their mass Cyg. A 0.7 solar mass star and spectral type K0 galactic nuclei. One of the recent distribution. This is only the tip orbits around a black hole of 12 solar masses in 6.5 and most spectacular discoveries has of the iceberg of an underlying days. Tidal forces deform the companion star and been the demonstration of the population that is estimated to pull off material from its photosphere, which falls towards the black hole forming an accretion disk. presence of a supermassive black comprise several thousand X-ray Courtesy of Rob Hynes. hole at the centre of our galaxy binaries in a state of “hibernation” Sagittarius A. Using adaptive optics (they do not emit X-rays). It is technology with the Very Large important to discover new X-ray Telescope (ESO, Chile), it has been binaries to enlarge the known sample possible to directly measure the of black holes. The second problem orbit of several stars around is to resolve whether ULXs, detected Sagittarius A. The presence of a in nearby galaxies, contain black supermassive black hole is the only holes of 100-1,000 solar masses. In possible explanation for that that case, we would be talking about extremely high concentration the unknown links between of matter in such a small volume. stellar-mass black holes and 30 Sociedad Española de Astronomía
supermassive black holes in galaxy Figure 2. Radial velocity curve of cores. This demonstration would 200 the companion star in V404 Cyg. It only be possible through dynamic shows the radial velocity variation of the K0 star due to the gravitational studies similar to the one we did with effect of the black hole. V404 Cyg. 0
How did it influence your
professional career? Have you (km/s) Velocity Radial -200 continued in that line of work? Has 6,5 days it opened new perspectives or later did you dedicate yourself to other 0 0,5 1 topics? Orbital phase This work has had a decisive influence on my career. It opened the door to a post-doctoral contract at the University of Oxford, where there used to be one of the strongest accretion disks at different timescales, hole.” Also, for some time after the European groups in X-ray binaries. from seconds to years. publication of this paper, I received Since then, I have continued my many emails and some manuscripts research in this type of objects. We Do you have any anecdote related from different parts of the world have revealed the nature of these to this paper’s gestation and asking for my opinion of quite compact objects with the discovery publication that you think is worth elaborate physical theories or trying of four additional black holes with telling? to convince me that the Theory of masses over 5 solar masses as well as I discovered the black hole during General Relativity was wrong. measuring neutron star masses. We the last year of my thesis, I had have also developed new techniques already finished my three-year to measure masses using fluorescent working contract at IAC and I was A 6.5-DAY PERIODICITY IN THE RECURRENT NOVA V404 emission produced by the irradiation unemployed. That event gave rise CYGNI IMPLYING THE PRESENCE OF A BLACK HOLE of the companion star. I have also to sensational news headlines of the J. CASARES, P.A. CHARLES AND T. N AYLOR dedicated part of my time to study type: “Spanish unemployed 1992, NATURE, 355, 614 the properties and behaviour of researcher discovers the first black 31
Eduardo Battaner López Departamento de Física de la Tierra y del Cosmos Universidad de Granada
What was the problem you had derived from kinematic most brilliant hypotheses of modern to face? measurements of the galaxy’s gas cosmology. We answered the critics Spiral galaxies rotate “too fast” and (measured in radio wavelengths). The in a more extended paper the rotation does not fall off with gas is very ionized. As in laboratory in a different journal; we wrote distance as occurs with planets. In plasma, the movement of this ionized an extensive review paper in another order to explain this “rotation curve” gas modifies the magnetic field and one and settled the issue, turning we resort to the hypothesis that a the magnetic field modifies the our attention to other research galaxy has a dark matter halo, which movement. topics. cannot be seen. Dark matter must be We determined that a centripetal Since then, there have been some ten times more massive and magnetic force could explain important advances. The magnetic extend about ten times further than the rotation. A classical field of the Milky Way and other visible matter and its nature is magnetohydrodynamic explanation was galaxies has been precisely measured. unknown. According to this used instead of the more exotic ones Its distribution is the one that we hypothesis, the most orthodox, based on dark matter. The existence of assumed to explain the rotation. We we do not know either the mass of dark matter was not denied, but it was have just highlighted this in a recent the galaxy, or its size or composition. not in the galaxies; rather the galaxies paper. were in the dark matter. Despite confirming a prediction What was the solution to this made 10 years ago, the dark matter problem and the contribution Since the paper was published, have hypothesis still prevails. However, this paper made to the area of there been significant advances it is acknowledged that the magnetic expertise in which it is framed? in this specific area? field cannot be ignored in The rotation of spiral galaxies at large Reactions to this paper were explanations of the rotation distances from the centre can be fierce. We had questioned one of the curve of spiral galaxies. 33 Astronomy made in Spain
Best fit: Axisymmetric Model Which are the main problems in this magnetism in intergalactic, extragalactic area of Astrophysics and what are the and pre-galactic media. In view of the expected discoveries in the coming new measurements of the magnetic field years? of the Milky Way, we have revisited this The established hierarchical dark area of research recently. matter models explain many things
0 179 notably well, but they do not Do you have any anecdote related to adequately explain the rotation curves this paper’s gestation and publication Figure 1. Predictions of a galactic magnetic field of spiral galaxies precisely. The Galaxy’s that you think is worth telling? model from Beatriz Ruiz’s thesis, directed by J. A. magnetic field is going to be very well The paper published in Nature was Rubiño and the author. determined with two future signed by Battaner, Garrido, Membrado experiments: Planck (space mission to and Florido. But Garrido, Membrado measure the Cosmic Microwave and Florido were the names of the co- Background) and the SKA (Square authors; don’t think these are undeserved Kilometer Array, a one square epithets to my person! (Translator’s kilometre array of radio antennas). note: Play on words, in Spanish Garrido, Membrado and Florido are How did it influence your surnames but also mean “handsome”, professional career? Have you “shrewd”, and “the elite” or continued in that line of work? Has “flowery”.) it opened new perspectives or later did you dedicate yourself to other topics? MAGNETIC FIELDS AS AN ALTERNATIVE EXPLANATION As I have already mentioned, I FOR THE ROTATION CURVES OF SPIRAL GALAXIES dedicated my attention to other topics. E. BATTANER, J.L. GARRIDO, M. MEMBRADO Figure 2. Image of the Planck observatory, a I felt it was better to wait. I have AND E. FLORIDO European Space Agency mission, launched in May worked in subjects related to 1992, NATURE, 360, 652 2009, which is allowing us, among other objectives, to gain a deeper knowledge of the magnetic field of our Galaxy. 34 Evencio Mediavilla Gradolph Instituto de Astrofísica de Canarias (Tenerife)
What was the problem you had or integral field spectroscopy. This Regarding the scientific results, to face? technique decomposes the focal plane I would like to say that, seen from the Kinematic studies of extended objects, into discrete elements (galaxy pieces), present perspective, it was one of such as galaxies, were done at that time transporting and aligning these the first papers where direct kinematic with inappropriate and laborious discrete elements in the spectrograph evidence for galaxy merging were sequential techniques, such as moving grating to obtain one spectrum of shown, very much in the line of the the slit over the object in successive each surface element of the galaxy. ideas about the hierarchical exposures. This method was subject to We used optical fibers to make the formation, although this was not systematic errors (some very important decomposition, and reformatting of the main approach of the paper. ones such as differential atmospheric the focal plane. Actually, this solution refraction) and to changes in the required a huge amount of laboratory Since the paper was published, have observational conditions at the time work, building several instruments there been significant advances of the exposure (changes of seeing, and prototypes, developing in this specific area? extinction, air mass, etc.). As a result, programmes for data reduction and At that time, there were three galaxy velocity maps in the optical were analysis, publishing papers which international groups with operational scarce and potentially unreliable. demonstrated the possibilities of this instruments (SILFID, TIGER, new, at the time, technique. The HEXAFLEX). The technique What was the solution to this publication of the paper about NGC belonged to these pioneering groups, problem and the contribution 2237 in the very prestigious journal of which we were part, and we had to this paper made to the area of Nature had a demonstrative effect: develop every application we needed. expertise in which it is framed? our instruments and new analysis Today, almost every telescope is (or is The solution was to develop a new techniques were innovative and planned to be) equipped with an technique, known as 3D spectroscopy reliable. instrument to perform 3D 35 Astronomy made in Spain
20 spectroscopy. For instance, the the truth is that the time when we 10 integral field spectrograph were starting was very special (the
0 HARMONI has been studied for the new ideas in the design of the (arcsec) δ
E-ELT (European Extremely Large technique could have a global -10 Telescope). We are part of the impact). -20 20 Spanish contribution to this Today, the technique is developed
10 instrument study. enough and the challenge is to build instruments with better performance. 0 (arcsec)
δ Which are the main problems This implies a technological -10 in this area of Astrophysics qualification which must be shared -20 20 10 0 -10 -20 20 10 0 -10 -20 and what are the expected by many members of large teams α (arcsec) α (arcsec) discoveries in the coming years? (that I find less motivating). Actually, 3D spectroscopy has passed Figure 1. Velocity and intensity maps of the Seyfert from being solely a resource of a very Do you have any anecdote related galaxy NGC 5033 obtained with INTEGRAL few experts to being a technique to this paper’s gestation and (it was front page of Astronomy and Astrophysics, widely used, as are CCD imaging or publication that you think is worth vol. 433). the classical grating spectroscopy. The telling? technique is expected to contribute The truth is that at that time, our to making big discoveries in all areas work was a doubly unusual paper for of astrophysics. Nature as it was based on an instrumental technique, and it was How did it influence your written by a team of solely Spanish professional career? Have you researchers. continued in that line of work? Has it opened new perspectives or later did you dedicate yourself to other EVIDENCE FOR AN OFFSET ACTIVE NUCLEUS IN THE topics? SEYFERT GALAXY NGC3227 Although we have always been very E. MEDIAVILLA AND S. ARRIBAS active in this field (now we 1993, NATURE, 365, 420 participate in HARMONI for the E-ELT, as we mentioned above), 36 Juan María Marcaide Osoro Departament d’Astronomia i Astrofísica Universitat de València
The papers in Nature and Science in We had previously worked, for other were formed and the competition was 1995 correspond to two phases of the purposes, on radio supernovae, but the fierce. The time allocation committees same research. The first one reports SN1993J explosion in the galaxy M81 finally decided to share the resources the discovery of the shell-like structure offered a unique opportunity. The between the groups in a fair way, each of the radio emission of supernova emission was relatively strong and the time demanding results to each of the SN1993J from VLBI observations distance to the supernova was relatively teams. Working from Spain, at the made on day 239 after explosion, and small. beginning the most difficult thing was the second one reports the expansion We could resolve its spatial structure. to remain in the race without being of that structure over a year -the first We quickly realized that it could be thrown out. The other team, with more supernova expansion “movie” ever. observed for more than a decade and American members (ours was more They are complementary. its evolution with time could be European rooted, but both had accurately determined... a luxury! scientists from many countries) was What was the problem you had a powerful one. The only way for us to to face? What was the solution to this survive was to succeed making the key The determination of the emission problem and the contribution these contributions before them. structure of a radio supernova and its papers made to the area of expertise We worked hard and were lucky. quick temporal evolution, and the in which it is framed? These papers showed the self-similar comparison of the results with the International resources to carry out this evolution of a spherical shell structure. predictions of the standard model research were only available in They confirmed the standard model that had been proposed ten years competition for just one instrument and the scientific contributions were earlier. In other words, our problem (the global Very Long Baseline unique. Together with another paper was to make the first movie of a radio Interferometry Network, Global VLBI in 1997 where we presented the supernova evolution. Network). Two large international teams deceleration of the expansion, they 37 Astronomy made in Spain
the expansion appears to be slightly different when observed at 6 cm and 18 cm. We found that there are instrumental and physical effects which make the measured expansion to be not exactly the same using 6 cm and 18 cm wavelengths. Nobody had thought of this before. It also showed that the other team may not have performed the analysis correctly as they have not detected this effect. Numerical simulations of the radiosupernova emission, absorption by the ejecta, and instrumental effects are capable of explaining not Figure 1. Evolution of the expansion of supernova SN1993J over a decade. only the discovery but can also simultaneously (and wonderfully) fit the radio light curves and the VLBI were the best contributions in this details of the expansion of the results. research field. The other group started supernova. We have also tried to to publish their contributions around understand how the emission that Which are the main problems the year 2000 (some of them we observe is generated. We have in this area of Astrophysics contradict our more recent results). done more than 30 observations and what are the expected Before then, and probably after, we led with the Global VLBI Network over discoveries in the coming years? this research. 14 years. The other team has done a This field of Astrophysics has a similar amount. Eventually we have fundamental problem: Radio Since the papers were published, analyzed the whole set of 69 supernovae explode either too far have there been significant advances observing epochs. away or they are not strong enough in this specific area? In my opinion the most significant microwave emitters to be able to study Since then, we have been working advance took place when we them in detail, despite of using the tirelessly trying to understand subtle discovered (published in 2009) that largest radio telescopes in the world. 38 Spanish Astronomical Society
Therefore, it has only been possible to Do you have any anecdote related to publication no anecdotes happened that study very few supernovae, less than these papers’ gestation and publication are worth mentioning. Perhaps I could a dozen in total, and none with the that you think is worth telling? mention a little one. Before the image detail of SN1993J. Perhaps the best one happened at the of the supernova expansion came out in very beginning I almost missed all the Science, Sir Martin Rees had already How did they influence your options to lead this research because for included it in his last book Gravity’s professional career? Have you more than a week I did not hear about Fatal Attraction of the collection continued in that line of work? the SN1993J explosion. I had Scientific American. I had informally Have they opened new perspectives practically been locked-up at home, passed the image to him during a visit or later did you dedicate yourself for almost a week, correcting from of mine to the Institute of Astronomy in to other topics? beginning to end the first draft of a Cambridge, and he asked me then if he I had previously written scientific PhD thesis of one of my students. could use it (he did not tell me what contributions in other areas (quasars, I learned about the event when I saw for). I told him that he could and that active galactic nuclei, graviational a photograph in El País newspaper. I was expecting to see it soon in Science. lenses, Galactic Centre, astrometry, I immediately called a Dutch colleague We almost had a copyright conflict! etc. I had even published in Nature who confirmed to me that radio Kidding. and Science four times before emission had been detected that very returning to Spain.) Almost all of same night in Cambridge. That was our these publications had the common starting point. The fact that the DISCOVERY OF SHELL-LIKE RADIO-STRUCTURE denominator of the use of the VLBI microwave emission is always delayed IN SUPERNOVA 1993J technique. This VLBI research on with respect to the visible emission was J.M. MARCAIDE, A. ALBERDI, E. ROS, P. DIAMOND the supernova SN1993J led me very helful for me this time. Well, AND 19 CO-AUTHORS towards radio supernovae studies. maybe I took the corrections of that 1995, NATURE, 373, 44 I am still actively pursuing this type PhD thesis draft too seriously. Naturally, of research. we managed to get the resources because EXPANSION OF SUPERNOVA 1993J important colleagues fully supported J.M. MARCAIDE, A. ALBERDI, E. ROS, P. DIAMOND our innitiative. I am very grateful AND 11 CO-AUTHORS to them. During the gestation and 1995, SCIENCE, 270, 1475 39
Vicent Martínez García Observatori Astronòmic Universitat de València
What was the problem you had average, the number of galaxies in a to a more homogeneous distribution to face? sphere of radius r centred on a given of galaxies in space is observed. It is known, since Edwin Hubble’s galaxy grows proportionally as r first observations in the thirties, that raised to a certain exponent which What was the solution to this galaxies are not randomly distributed. we call correlation dimension. For the problem and the contribution these Already in the eighties, the first distribution of galaxies and a papers made to the area of expertise three-dimensional galactic surveys significan range of scales, this in which it is framed? were carried out. That is to say, dimension is approximately 2, a value At the time when the 1999 Science those, which besides the position that is significantly different from 3 paper was published there was a of the galaxies in the celestial sphere which would be expected for a certain debate within the scientific contain information about their homogeneous distribution (in that community about the fractal nature distances (measured from its case the number of galaxies would of galaxy distribution at small scales redshift). These three-dimensional grow proportionally with the volume and the existence of a limit at larger maps of the cosmic macrostructure of the sphere). On the other hand, scales. A group of scientists traced by the distribution of galaxies present cosmology is based in the maintained that, with the show a texture characterized by large Cosmological Principle which states observational data available, the filaments, galactic clusters and that the large-scale Universe must be fractal structure did not seem to superclusters, flat structures like big homogeneous (there are no preferred break and, therefore, no transition to walls, which delimit regions locations) and isotropic (there are no homogeneity was observed. apparently empty of luminous preferred directions). In this paper we The paper proved that, even matter. This cosmic web can be tried to solve the problem of the though galactic surveys were not yet characterized, at scales which are not determination of the scale at which large enough, a gradual transition to too large, by its fractal structure. On the transition from a fractal regime a homogeneous distribution of the 41 Astronomy made in Spain
luminous matter was already evident scales close to 500 million light-years at scales of the order of 200 million which agree fairly well with the light-years. theories of cosmic structure formation. Since the papers were published, have there been significant advances Which are the main problems in in this specific area? this area of Astrophysics and what Certainly, much deeper galactic are the expected discoveries in the surveys have been completed since, coming years? covering very wide regions of the sky One of the fundamental problems which contain hundreds of thousands is the precise measurement of of galaxies. The two most important the acoustic peak I mentioned in the are: The 2-degree field redshift survey previous question. The position of Figure 1. Distribution of galaxies in two sectors made with the multi-object this peak determines a characteristic of the sky centred on the Earth. The deepest sector spectrograph at the 3.9 m Anglo- distance whose precise measurement (the one below) reaches a distance of 3,000 million Australian telescope and the Sloan can give very valuable information light-years. The dots represent the position of 13,000 Digital Sky Survey made with a about the nature of what galaxies. Structures like filaments, walls and voids can be observed in both sectors but the size of these dedicated 2.5 m telescope in New cosmologists have called dark energy, structures is not larger in the deeper slice, as it would Mexico. Both galaxy catalogues have thought to be the dominant be expected in a fractal structure. been used to corroborate the gradual component of matter and energy in transition to a more homogeneous the Universe (70% would be dark distribution at the scales predicted in energy) that would be responsible my paper in Science. In fact, if we for the acceleration of the cosmic statistically study the clustering of expansion observed today. Projects galaxies by means of a two-point such as PAU (Physics of the correlation function, the latter shows Accelerating Universe), with the that the fractal behaviour at small objective to construct a survey of scales disappears at larger ones; it has more than 200 million galaxies using been even possible to prove the photometric techniques, can existence of a peak (a small local contribute to the solution of this maximum, called acoustic peak) at enigmatic energy. 42 Spanish Astronomical Society
Undoubtedly, another fundamental cosmic evolution, the nature of dark problem would be to know the energy through the study of baryonic details of cosmic evolution, in other oscillations, the detection and 10 words, how the distribution of morphological characterisation of (r) matter at different epochs since its larger cosmic structures: filaments formation gives us information about and galactic superclusters, etc. 1+ the physical processes which took place. The ALHAMBRA survey, Do you have any anecdote related 1 made with the 3.5 m telescope at to these papers’ gestation and 1 10 100 Calar Alto, has this scientific publication that you think is worth r(h-1 Mpc) objective; it will cover a sky area telling? equivalent to 20 times that of the full Yes, I have an interesting one Figure 2. The correlation function of galaxies for Moon, but it will have an concerning the 1999 paper. The different surveys shows a gradual transition from a unparalleled depth for such a large Science editor sent, as it always does, fractal regime with a correlation dimension of 2, to area. the paper to two different referees. a homogeneous distribution with a correlation Both were very positive but one of dimension of 3. How did they influence your them mentioned in his report that professional career? Have you Nature had recently published a continued in that line of work? similar paper. One of its authors was Have they opened new perspectives the British Royal Astronomer Sir or later did you dedicate yourself Martin Rees (The large scale to other topics? smoothness of the universe, Wu, Lahav The 1995 paper in Science was the and Rees, 1999, Nature, 397, 225). completion of an intensive period The paper cited my previous works. of activity that I had started with my But due to this fact, the editor of thesis. I keep on working on the Science chose not to publish my new study of the large-scale structure paper in the journal. Of course of the Universe but I have also been I accepted the decision, although I interested in other problems such as thought that my contributions were the extension of dark matter halos different and in a sense, more surrounding elliptical galaxies, convincing. During those weeks 43 Astronomy made in Spain
I was in touch with my British deserved to be published in Science colleague, Professor Peter Coles. because of its contribution to the MULTISCALING PROPERTIES OF LARGE SCALE STRUCTURE When I told him what had happened field. The editor sent Peter Coles’ IN THE UNIVERSE he asked me a few details, for letter to the original referees of my V.J. MARTÍNEZ, S. PAREDES, S. BORGANI AND P. C OLES example the name of the editor who paper asking them to check both 1995, SCIENCE, 269, 1245 was responsible for the decision. and give a considered opinion Later, I learnt that he wrote to her, about publishing my paper in IS THE UNIVERSE FRACTAL? identifying himself as the referee of Science. Both answers were V.J. MARTÍNEZ the paper published in Nature, favourable and, finally, the paper 1999, SCIENCE, 284, 445 stating that in his opinion, my paper was published.
44 Francisco J. Castander Serentill Institut de Ciències de l’Espai (CSIC-IEEC, Barcelona)
What was the problem you had fundamental for the study of the Since the paper was published, have to face? universe. Clusters are formed by there been significant advances The paper was published in the middle galaxies, hot gas and dark matter. in this specific area? of the nineties. At the time, we already Traditionally, clusters were detected by Since our paper was published, this had an idea of how galaxies and galaxy searching for overabundance of topic has experienced great advances. clusters had formed. Galaxy clusters are galaxies, which is not a very reliable On the one hand, the ROSAT satellite the largest structures observed and the method. With the arrival of X-ray continued to obtain data and in evolution of their abundance depends satellites it was possible to start subsequent years it was possible to considerably on the constituents of the detecting clusters through the X-ray analyse many more observations and to universe, and in particular, on the amount emission of the hot gas they contain. increase the number of clusters studied. of existing mass. The observational The first results showed a fast evolution Later, in 1999, two new X-ray measure of the mass in the universe was in the number of clusters, compared satellites were launched, XMM- one of the most important questions at with what was expected. Our work was Newton and Chandra, that to date are the time since it is a parameter which the first to use data from a new X-ray providing high quality data, which determines the geometry and global satellite ROSAT, launched in 1990, to allow us to study in detail galaxy evolution of the cosmos. study the evolution of cluster clusters and the evolution of their abundance. We found that the populations. Together with other What was the solution to this evolution in the number of clusters was cosmological probes like the Cosmic problem and the contribution inconsistent with the predictions based Microwave Background (CMB) and this paper made to the area of solely on gravitation and we supernovae, the clustering of galaxies expertise in which it is framed? highlighted the need to understand the allows us to know quite precisely the Galaxy clusters, and especially the behaviour of hot gas to be able to use composition of the universe and its evolution of their abundance, are clusters for the study of the universe. geometry. 45 Astronomy made in Spain
Which are the main problems How did it influence your in this area of Astrophysics professional career? Have you and what are the expected continued in that line of work? Has discoveries in the coming years? it opened new perspectives or later Today we know that our universe did you dedicate yourself to other comprises approximately 5% topics? ordinary matter, 20% dark matter I believe that the publication and 75% dark energy, which is of this paper at the end of my thesis accelerating the expansion of the enabled me to successfully obtain universe. Understanding dark matter post-doctoral positions, especially the and dark energy is one of the first one that allowed me to continue challenges of modern cosmology. my career in research. Since then, as During the last years, large projects well as galaxy clusters, I have worked Figure 1. False-colour image of the X-ray emission are being designed and developed to on other topics as the evolution of from the gas in the Coma galaxy cluster. analyse this problem with different galaxies, gravitational lensing, the observational techniques. One of cosmic X-ray background radiation, them is the study of galaxy clusters. Gamma-ray bursts, but always with This will be done with images in the the common aim of understanding visible wavelength range and with the structure and evolution of the hot gas studies in the radio and Universe. Now, I am involved in large X-rays. In particular, a new X-ray observational cosmology projects to satellite that will study the evolution study dark matter and dark energy, of galaxy clusters in more detail is using different techniques, including planned to be launched. galaxy clusters.
46 Spanish Astronomical Society
Do you have any anecdote related to this paper’s gestation and publication that you think is worth telling? We wrote this paper during the last year of my PhD in Cambridge. During the phase of external editing, I was doing the compulsory military service. When I did not have to be in barracks, I was going to work at LAEFF (Laboratorio de Astrofísica Espacial y Física Fundamental) in Madrid, to make corrections and modifications to my paper. I have always been grateful to them for their hospitality.
DEFICIT OF DISTANT X-RAY-EMITTING GALAXY CLUSTERS Figure 2. ROSAT is an acronym for Röentgen
AND IMPLICATIONS FOR CLUSTER EVOLUTION Satellite. This space mission provided a fundamental advance in our knowledge of the X-ray sky. F.J. CASTANDER, R.G. BOWER, R.S. ELLIS, A.
ARAGÓN-SALAMANCA AND 7 CO-AUTHORS
1995, NATURE, 377, 39
47
Rafael Rebolo López Instituto de Astrofísica de Canarias (Tenerife)
What was the problem you had of exoplanets at a time when we did object we found with characteristics to face? not know if either of these existed. typical of a brown dwarf, named Teide Proving the existence of brown Pléyades 1, had a spectral energy dwarfs, intermediate bodies between What was the solution to this distribution consistent with a spectral stars and giant planets. These dwarfs problem and the contribution type of M8 and a proper motion are similar in size to Jupiter, but this paper made to the area of consistent with that of the Pleiades according to theory, they would be expertise in which it is framed? stars. Using substellar evolution about 10 and 70 times denser. The paper in Nature proved the models, we concluded that their Already in the 1960s, there was existence of brown dwarfs in the characteristics could only be speculation about the existence of Pleiades Star Cluster, a region where understood if it was an object with a these objects; there were several good there had been many searches before mass lower than 65 times the mass of candidates but none of them was but they were unable to reach objects Jupiter, that is, a brown dwarf. Based conclusive. We knew that if brown with luminosities and temperatures on the statistics that we obtained, we dwarfs were very numerous in the that are sufficiently low as to conclude could already state in this work that Galaxy they could contribute to dark that the hydrogen burning limit had in the Pleiades cluster there could be matter. been crossed, this is the limit that hundreds of these objects and This was one of the motivations separates stars from brown dwarfs. thousands of them in the Galaxy. to search for them. It was also hoped Most of the previous searches were that they had atmospheric done using V and I filters but we Since the paper was published, have characteristics similar to those of decided to use the R and I filters, there been significant advances giant planets and, therefore, the based on what we expected from the in this specific area? detection of these characteristics spectral energy distribution of massive There have been enormous advances. could help us in the direct detection brown dwarfs in the cluster. The first Some months later, the discovery and 49 Astronomy made in Spain
1.4 1.2 1.0 .9 .8 .7 .6 .5 .1 .008.055 0 detection of the next brown dwarf was also published in Nature. This was Initial Li content identified as Gl 229 B, in this case the first brown dwarf orbiting a star. Our 3 Teide1 Calar 3 group identified other similar objects to Teide 1 in the Pleiades. The 2 following year, we already had an indication of the mass function in the cluster that effectively indicated that
log N(Li) PPl15 1 there were hundreds of these objects in the Pleiades. Presently we know several dozens and more are being 0 discovered. The brown dwarf mass function has been determined today in many clusters and in the solar neighbourhood. The evidence of the 7000 6000 5000 4000 3000 2000 existence of thousands of millions Teff (K) of brown dwarfs in the Galaxy is conclusive; there could even be Figure 1. Brown dwarfs Pleiades Teide 1 and Calar 3 (discovered a few months later) have preserved their initial as many as stars. lithium content. Each symbol shows the lithium abundance of an object (in a logarithmic scale) versus the Our group led the discovery of temperature of its atmosphere. It can be seen how the stars of the Pleiades cluster with masses below that of the brown dwarfs with increasingly low Sun have depleted their lithium content according to their mass, the smaller the mass the larger the depletion. In masses, detecting the first free-floating the stellar interiors, lithium nuclei are destroyed via proton collisions at a very high temperature and this can be drastic in lower-mass stars. However, it was expected that the brown dwarfs of the cluster had a very different planetary-mass objects in stellar clusters behaviour since they should not reach the necessary temperature for those collisions to break lithium nuclei. like the one in the Sigma Orionis star Spectroscopic observations carried out with the Keck telescope in November 1995 revealed that both Teide 1 cluster. We also discovered the second and Calar 3, the least luminous objects found in the Pleiades up to that date, confirmed what was expected for bona fide brown dwarfs.
50 Spanish Astronomical Society
brown dwarf orbiting a star, G 196-3B we will learn a lot about atmospheres Do you have any anecdote related (published in Science in 1998); at that in a very poorly explored domain to this paper’s gestation and time this object, with a mass 25 times which overlaps with the one of planet publication that you think is worth the mass of Jupiter, was the least temperatures like Venus and the telling? massive substellar object known. Earth. We discovered the object with the 80 cm IAC80 telescope at the beginning Which are the main problems How did it influence your of 1994; at the end of that year we in this area of Astrophysics professional career? Have you were able to obtain the spectrum that and what are the expected continued in that line of work? Has confirmed its nature with the 4.2 m discoveries in the coming years? it opened new perspectives or later William Herschel telescope. We sent Establishing how far down the mass did you dedicate yourself to other the paper for publication to Nature function the substellar domain topics? in May 1995 and we needed several extends, that is, the masses of the It had an important influence. This months to convince the referees that smallest objects that result from the work was crucial for the formation we had discovered a new class of fragmentation of the clouds of of a research group on brown dwarfs objects. Finally, it was published on interstellar material. In other words, at IAC. This group has produced 14 September 1995. Nature wrote at are there free-floating super-Jupiters dozens of papers that sum up the front page “Brown dwarfs exist - in the interstellar space? thousands of citations and it official”. Another problem of great interest is continues to be very active. I am the detection of low-temperature proud that the research of the group brown dwarfs; there must be hundreds members is recognised at an DISCOVERY OF A BROWN DWARF IN THE PLEIADES STAR in the solar neighbourhood with international level. In the last years CLUSTER atmospheric temperatures between we are directing our research towards R. REBOLO, M.R. ZAPATERO-OSORIO AND E.L. MARTÍN 300 and 500 Kelvin. We haven’t the area of exoplanets with the aim 1995, NATURE, 377, 129 discovered them yet. Detecting these of detecting Earth-like planets objects is an extraordinary challenge, around other stars.
51
Carlos Westendorp Plaza Instituto de Astrofísica de Canarias (Tenerife)
What was the problem you had penumbra, was the area where these back down to the Sun’s interior. This to face? phenomena converge and where we was expected but no one had been Trying to understand the manifestation were able to obtain new results. previously able to deduce this from on the solar surface of the magnetic observations until then. field generated in the Sun’s interior What was the solution to this was, and still is, a big challenge. The problem and the contribution Since the paper was published, enigma that we call “sunspots” that was this paper made to the area of have there been significant advances already known in ancient China led us expertise in which it is framed? in this specific area? to question our understanding of the Through the result of Basilio Ruiz After consulting experts like Basilio “measurement” concept in Physics. Cobo’s thesis and his later work, we and Valentín, they confirmed that the There are so many interacting managed to develop a computer study of the sunspot penumbra has phenomena (plasma, convection program which is used all over the aroused an enormous interest in recent movements, richness of the magnetic world. I was very lucky to be able to years. Initially, it was due to the field structures and all with supersonic apply this code to the observations discovery that the bright penumbral velocities of unknown origin and Valentín Martínez Pillet brought from filaments present a central darkening direction) that it is impossible to study the USA and with Jose Carlos del Toro (or “dark-core”) in 2002, using one without understanding the whole. Iniesta’s energy and inspiration, we observations from the new Swedish Some excellent sunspot observations obtained the first in-depth view of a Solar Tower. Many groups worked on that provided a lot of detailed sunspot in all its splendour. It revealed the problem to find a physical information enabled us to take a step the complexity of the magnetic field explanation for the phenomenon. It forward from the traditional methods. over the solar surface, together with was thought to be very closely related The complex external filamentary velocities that showed that they to the structure of the filaments and structure of the spot, called the followed the magnetic field and looped the velocity field which constitutes the 53 Astronomy made in Spain
so-called Evershed flow (named after the Magnetic Field Strength (G) 25 180º discoverer in 1909). Finally, two 20 log ( 5)= -2.8 135º possible scenarios have prevailed: The 15 90º uncombed scenario in which the Mn 10 Evershed flow is produced through 45º more horizontal tubes and with a 5 log ( 5)= -1.5 weaker field strength embedded in a 0 0º 0 5 10 15 20 25 30 more vertical and intense field, and the Mn gappy scenario, where the bright filaments would be the observational Figure 2. Map of the magnetic field inclination in a log ( 5)=0.0 typical sunspot (colour coded), close to the centre of counterpart of convective penetrations the disk (direction indicted by the arrow). Velocities in the penumbra. Both models seem to are represented by continuous contour lines (in black partially explain the observational towards the observer, in white they move away from properties. The uncombed model the observer). It shows how velocities are detected 0 750 1.500 2.250 3.000 seems to fit the results on the moving away from the observer before the end of the sunspot (dotted line) and where the field is horizontal spectropolarimetric inversions better, Figure 1. Intensity of the magnetic field, colour or even loops back onto the surface (it shows more with the presence of a non-zero net coded, for three photospheric layers of a sunspot, from than 90º with respect to the horizontal axis). circular polarisation and with the the deepest to the most superficial. The arrows show Evershed flow. The gappy model seems the magnetic field vector (intensity, zenithal angle to explain the brightness of the and azimuth). The dark lines show the limits the umbra/penumbra and the sunspot with the penumbra more easily. surrounding Sun in calm. Additionally, the study of the magnetic fields in the moat (the region surrounding the spots) and the plasma velocities in those areas have confirmed the discoveries we published in our paper, in the sense that movements of materials in sea-serpent-like structures Figure 3. Simplified representation of the suggested are observed, which are nothing more structure of the penumbra and the velocity flux than the extension of penumbral (Evershed effect). filaments. 54 Spanish Astronomical Society
Which are the main problems in this to be good. Unfortunately, for this you mass media. When some of them came area of Astrophysics and what are the have to publish in magazines where the to the institute, in front of a TV expected discoveries in the coming scientific interest is not the most camera and with a microphone, I had years? important thing, as confirmed recently to answer the question: “…but, what The main problems in this field in Nature where they do not seem to have you discovered?” Trying to explain continue to be the clarification of the be interested in Solar Physics because all the work behind a process which structure of penumbral filaments and it does not provide them with a high took several years, especially taking into their relationship with both the number of citations. It is still a hard account not only the years in which Evershed flow and the brightness of the work to reach the public, to whom I participated but all the previous work penumbra. There is also the question we undoubtedly should dedicate more that constituted the base of this result, of the MMF (moving magnetic features) economical and human resources as was a really big challenge. Actually, and their connection with the it is an inherent part of our work. more than a “discovery”, if this result penumbra and the magnetic flux The impact of this work also made was a milestone (and it seems that time elimination mechanisms of the spot. more difficult the decision I had taken is proving it to be), the important We also need to find an explanation before finishing my thesis to change thing is that it represents the success for the structure and dynamics of the my career path to my other passion of a good team. umbral dots and umbral flashes, as well of informatics. Working close to the as the distribution of sunspots and the people who made it possible and dynamo mechanism (oscillation in knowing that the work is still cited EVIDENCE FOR A DOWNWARD MASS FLUX IN THE the Sun’s magnetic field). in international conferences and that PENUMBRAL REGION OF A SUNSPOT some of my colleagues are still working C. WESTENDORP, J.C. DEL TORO INIESTA, B. RUIZ How did it influence your on it gives me a great satisfaction. COBO, V. MARTÍNEZ PILLET, B.W. LITES professional career? Have you AND A. SKUMANISH continued in that line of work? Has Do you have any anecdote related 1997, NATURE, 389, 47 it opened new perspectives or later to this paper’s gestation and did you dedicate yourself to other publication that you think is worth topics? telling? I learnt how the efforts of a great and Although the results were known by well balanced team can bring a reward, the international scientific community, as well as that in science, you need to it was only after the publication of this be good but you also have to seem paper that we were contacted by the 55
Benjamín Montesinos Comino Centro de Astrobiología (CSIC-INTA, Madrid)
What was the problem you had At the beginning of the nineties higher pressure to the regions with to face? there was no satisfactory explanation lower pressure. This works in a In 1909 the British astronomer John for this phenomenon, and after some similar way to when we want to Evershed (1864-1956), who was at the preparatory work, John H. Thomas empty a liquid container with a thin Kodaikanal Solar Observatory in India, and I decided to propose a plausible tube: to start emptying it out we discovered that the spectral lines model that explained the observed suck from one end while the other originated in the penumbral filaments features of this phenomenon and one is submerged in the liquid. This of sunspots were not at their rest predicted some others. explanation, which seems positions but showed a Doppler shift. qualitatively logic and simple, is The displacement of the spectral What was the solution to this extremely complicated to manage lines from their normal positions problem and the contribution from the numerical modelling point indicate that the material producing this paper made to the area of of view, as it requires the simulation them is moving towards us if the expertise in which it is framed? of the various phenomena, stresses, shift is towards the blue, or moving The solution to the problem lies in pressures, etc., that a flux tube (the away from us if the shift is towards what is known as “siphon flows” in penumbral filament) suffers the red. This phenomenon observed thin magnetic flux tubes. Basically, submerged in a magnetized in the filaments was called “Evershed this model assumes that sunspot atmosphere (the magnetic field of the effect” and was interpreted as a mass penumbral filaments act like spot). Basically, our work was the flow in the penumbra of sunspots, magnetic flux tubes which channel first one that managed to successfully from the regions close to the sunspot gas flows. If the pressure in one explain many of the features of the umbra (the darker central part) of the footpoints of the tube is lower Evershed flow (velocities, densities, towards the outer parts; this flow than at the other footpoint, the gas magnetic fields, lengths, shapes and is called “Evershed flow”. will flow from the regions with heights of the tubes). 57 Astronomy made in Spain
Since the paper was published, have paper in Nature, several there been significant advances interpretations arose attempting to in this specific area? reproduce the observed timescales in In the last decade there have been the flow behaviour. considerable observational advances which are contributing towards Which are the main problems in this a better knowledge of this area of Astrophysics and what are phenomenon. One of the the expected discoveries fundamental challenges of solar in the coming years? observations is to obtain the best Despite being the closest star to us possible spatial resolution, that is, to —or precisely for this reason!— there try to discriminate the properties of are many phenomena, not only in a given phenomenon in increasingly the sunspots but globally in the Figure 1. Sunspots showing the umbra and small surface elements. Recently, entire Sun, that need a theoretical penumbral filaments well differentiated with respect observations of the Evershed effect model which is still incomplete. On to the photospheric granulation. Courtesy of the have been obtained with a resolution the other hand, observations become Royal Swedish Academy of Sciences. of 0.2 arc seconds using the Solar of increasing better quality and that Telescope of the Royal Swedish helps to put strong constraints on the Academy of Sciences, at the Roque theoretical developments. de los Muchachos Observatory, and In the specific field of sunspots, the Japanese space observatory helioseismology (the study of solar Hinode has provided data of the oscillations) is providing data small scale structure of this mass regarding the structure of sunspots flow. From the theoretical point of below the photosphere and that will view there have been advances in the help us to better understand the interpretation of the time variations complex energy balance mechanisms. of the Evershed effect: our model is If we consider the Sun globally, steady, that is, the equations that I think there are two intricate and describe the phenomenon do not difficult problems, although little by depend on time and, in the years little progress is being made based on following the publication of this the established models: The first one 58 Spanish Astronomical Society
is coronal heating and the second one in about 30 solar-type stars; these is the origin of solar cycles. The fact cycles are similar to the 11-year cycle that in both cases three-dimensional of the Sun. Currently, my research is models are needed and that they have almost centred in the physics of young to include complex stars (between 1 to 10 million years) magnetohydrodynamic formalisms with protoplanetary disks made of gas and nonlinear physics make these and dust, and of older main-sequence problems extremely hard to tackle. stars surrounded by debris disks. Figure 2. Sketch of the filamentary structure How did it influence your Do you have any anecdote related of a sunspot. The umbra is modelled as a thin professional career? Have you to this paper’s gestation and magnetic tube bundle and the penumbral filaments are extensions of those tubes which emerge over continued in that line of work? Has publication that you think is worth the photosphere. The Evershed flow would be it opened new perspectives or later telling? channelled through those thin filaments. did you dedicate yourself to other I started to work on this area by topics? chance. In 1988 I was working on Obviously all the work I did together other issues with a post-doctoral with Professor Thomas has been very contract at the Physics Department important for my professional career. at Oxford University. That year John It opened a new area of research and H. Thomas (Jack), a professor from I learnt a lot, both in the theoretical Rochester University (New York), aspects and in the field of numerical arrived to join our group for a calculations associated with the sabbatical stay. After talking one day, solution of this problem. After the we started to do some simple publication of this paper in Nature, calculations about the mass flow which for us really finalised the behaviour in thin magnetic tubes. problem, I have not continued From there we started a working on this specific issue, but in collaboration, which lasts until today. an area within the so-called “Solar- The simple calculation we performed stellar connection” which is the in 1988 was becoming more and modelling of the activity cycles more complicated and culminated in observed over the last four decades 1997 with the publication of the 59 Astronomy made in Spain
paper in Nature. As it can be seen, From the beginning of the and his wife have also visited me in Spain the gestation lasted almost 10 years! collaboration with Jack, I started a and I will not forget their astonishment I was surprised to be able to publish friendship with him and his family, when they saw the Alhambra, the Alcázar a paper in Nature that was essentially which for me is as important as our de Sevilla, the Mezquita de Córdoba... theoretical, although the model was scientific interaction. I have visited and obviously, the Easter processions successfully compared to Rochester several times and I have always during a trip to Andalucía in1993. observations. In any case, it gave a found hospitality at Thomas’ home. I satisfactory answer to a problem that went to visit the Niagara Falls for the first had remained unresolved for 90 yeas time with them, to buy products to an THE EVERSHED EFFECT IN SUNSPOTS AS A SIPHON FLOW and perhaps, this was the important Amish community in the state of New ALONG A MAGNETIC FLUX TUBE fact when the journal accepted this York, I learnt how to sail in a small boat B. MONTESINOS AND J.H. THOMAS paper. and to water-ski at the Keuka Lake. Jack 1997, NATURE, 390, 485
60 Ramón Oliver Herrero Departament de Física Universitat de les Illes Balears (Palma de Mallorca)
What was the problem you had varies). Therefore, the problem was: an increase in the number to face? why do high-energy flares show this of flares. Flares are explosive phenomena periodicity? Why does this Using wavelets, which enable the occurring in the solar atmosphere periodicity coincide with the precise determination of the time that release energy and particles maximum of solar activity? and frequency of a phenomenon, which propagate through the we proved unmistakably that during interplanetary medium. Particles What was the solution to this 1980-1984 the periodicity seen in ejected in very energetic flares reach problem and the contribution flares was also simultaneously seen the Earth producing the Aurora this paper made to the area of in sunspot areas. This work provided Borealis and causing damage to expertise in which it is framed? the first explanation of the reason the electrical equipment onboard A previous study on the behaviour for this periodicity, leaving open the satellites orbiting the Earth. Between of sunspot regions carried out by question of why the magnetic flux 1980 and 1984, the Solar Maximum our group concluded that they also emerged periodically near the solar Mission satellite observed that the showed a five-month periodicity. activity maximum. number of high-energy flares Since the area of a sunspot is increased every five months, although directly related to the amount of Since the paper was published, have the mechanism that triggered this magnetic flux that originates in the there been significant advances periodical increase was unknown. Sun’s interior and emerges through in this specific area? Likewise, this periodicity appeared the surface, the probable cause of the After the publication, we analysed during the maximum of the solar periodic nature of solar flares is the available data on the activity cycle (11-year cycle during the periodic emergence of magnetic photospheric magnetic flux and which the number of different flux causing reconnections with verified the exact correlation between phenomena such as sunspots or flares the existing one, thus stimulating the periodic impulses of magnetic 61 Astronomy made in Spain
190 10 flux and flares, unmistakably 180 8 confirming their correspondence. 170 6 This periodicity has also been 160 detected, with more or less intensity, 4 150 around some of the maxima of the 2 140 subsequent solar activity cycles. Some 1920 1935 1949 1964 1978 1993 Power/Color Time (year) (a.u.) theoretical explanations of why the magnetic flux emerges in a periodical 190 way have been proposed but they are 180 4 not convincing. 170 3 160 2 Which are the main problems 150 1 in this area of Astrophysics and 140 1980 1981 1982 1983 19784 1985 Power/Color what are the expected discoveries Time (year) (a.u.) in the coming years? 190 The fundamental problem is to 3,0 180 obtain a perfect understanding of the 2, 170 2,0 way the magnetic flux emerges from 160 1,5 the Sun. Presently, and thanks to the 150 1,0 availability of supercomputers, 140 0,5 numerical codes and visualization 1980 1981 1982 1983 19784 1985 Power/Color (a.u.) tools, it is possible to carry out Time (year) highly sophisticated numerical simulations to understand Figure 1. Wavelet analysis of the sunspot area time series. The year is indicated in the horizontal axis and the emergence process from the the period in the vertical axis. An intense periodicity in a specific moment of time is shown as a red-colour convection zone to the corona. spot in the corresponding year and period. Upper image: White vertical lines show the solar activity minimum epochs. The 160-day periodicity appears significantly near the maxima of cycles 16 to 21. Middle image: Zoom-in of the period 1980-1985 showing the time interval, around the maximum of cycle 21, where the periodicity is evident. Lower image: Precise determination of the period. 62 Spanish Astronomical Society
How did it influence your professional suitable technique, i.e. the wavelet career? Have you continued in that analysis, prevented us from testing line of work? Has it opened new the veracity of the hypothesis. perspectives or later did you dedicate Finally, in 1998 we were able to use yourself to other topics? an analysis program based on wavelets After the publication of this paper we that allowed us to confirm this have continued working in this and hypothesis. We also believe that it other lines of work. Recently we have was one of the first wavelets analysis obtained some theoretical results applications to a solar physics which allowed us to explain the problem. periodic emergence of magnetic flux from the tachocline (a very thin layer in the Sun’s interior which seems EMERGENCE OF MAGNETIC FLUX ON THE SUN AS THE to be directly related to the generation CAUSE OF A 158- DAY PERIODICITY IN SUNSPOT AREAS of the magnetic field emerging R. OLIVER, J.L. BALLESTER AND F. B AUDIN through the photosphere) and why 1998, NATURE, 394, 552 this emergence appears predominantly around the maximum of solar activity.
Do you have any anecdote related to this paper’s gestation and publication that you think is worth telling? The hypothesis at the basis of our work was formulated around 1990, but the lack or ignorance of a
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José Cernicharo Quintanilla Centro de Astrobiología (CSIC-INTA, Madrid)
What was the problem you had second problem, strongly linked to Nebula?”. The UV light of the to face? the first one, was how to access the central star has photoevaporated The interpretation of the formation innermost regions of the star the most external layers of the mechanisms of stars in giant formation clouds. The results surrounding clouds (the arms of the molecular clouds was one of my to these problems were published Trifid) inducing strong pressure and fields of work when we published the in the two Science paper of which density gradients and a second first paper in Science. Until that time I was the first author. episode of formation of less massive it was difficul to carry out detailed stars that populate the dark regions studies because most of the What was the solution to this of the nebula. information on the physical problem and the contribution With respect to the second paper, conditions of the gas had been this paper made to the area we realized that the bands obtained in the milimiter and radio of expertise in which it is framed? corresponding to the frozen grains domains. The advent of the Infrared Our first surprise during the study left opened some windows with less Space Observatory satellite (ISO) of the Trifid was to see that there were absorption in the spectrum. We allowed us to analyse the fine- a large amount of young objects in the observed with ISOCAM (one of structure emission lines from carbon boundary between the ionized and the instruments of ISO) one of the and oxygen and also to obtain data neutral gas, the photodissociation prototypical regions with embedded on the emission from dust grains and region in astronomical jargon. The young stars, and we managed to see its distribution in the Trifid nebula. data indicated that most likely there directly the youngest objects The choice of this object was done were a second and a third generation through those windows. The title according to its size, appropriate of less massive stars; this originated of the paper was “Windows Through for the angular resolution of the the title of the paper “Induced the Dusty Disks Surrounding the instruments on board ISO. The Massive Star Formation in the Trifid Youngest Low-Mass Protostellar 65 Astronomy made in Spain
Figure 1. Image of the SW region of the Trifid Nebula taken with a filter that allows us to observed the emission by sulfur atoms singly ionized. The observation was taken with the Nordic Optical Telescope (NOT) at the Observatorio del Roque de los Muchachos (La Palma). With the letter ‘J’ we have marked the position of the jet emerging from the upper part of the globule. The region marked with ‘B’ indicates a shock front caused by the jet. In the inset at the top right we show a mosaic of H· images obtained with the IAC80 telescope at the Observatorio del Teide (Tenerife). The mosaic covers the whole nebula and shows in colour the area observed on the NOT.
Objects”.The conclusion, confirmed Since the paper was published, a few years later with Spitzer data, have there been significant advances was that even with absorption in the in this specific area? optical larger than 100 magnitudes, The advances have been enormous. The it was possible to observe the observatory Spitzer started working innermost layers due to the change shortly after our two publications of the absorption with wavelength. appeared in the journal. Spitzer data We derived a size of 3-4 AU and are of very high quality and they have a dust temperature of 300-400 K. shown the complexity of the physical Most probably we were seeing the processes involved in the evolution surface area of the protoplanetary of gas and dust and then in star disk illuminated by the central formation. We still need to study star. those objects with high angular 66 Spanish Astronomical Society
resolution and a larger sensitivity. In or rocky— planets is one of the objects. I think this is a very exciting this context, the space observatory fundamental problems in this field. field and the new interferometer Herschel is already making spectacular Knowing how the chemical ALMA will open a completely new and contributions to the observation of composition of the gas changes with original vision on the evolution of gas the universe in the far infrared and time, understanding how the gas is from the very first moment of the disk submillimiter domains. We expect a deposited in the dust grains during formation up to the formation of the quantitative step forward because the the first stages of the formation of a first planetesimals that later will instruments are much more sensitive star, studyng the chemical processes originate the planets. We are currently than those on ISO and Spitzer, and of the gas occurring in the surface of very limited in sensitivity and angular the telescope has a diameter of 3.5 the grains, its further evaporation and resolution to understand the subtle meters instead of 0.6 and 1.0 meters the accretion onto the planetesimal chemical processes originating the of those two space platforms. are stories still to be written. We are in complexity and the properties of the a trully exciting time for Astrophysics. early planetary atmospheres. My Which are the main problems Spanish astronomers are very well opinion is that ALMA will be a tool in this area of Astrophysics and positioned to participate in this that will provide us endless discoveries what are the expected discoveries endeavour. The data we have now in in the field of star and planet in the coming years? our hands are limited and so recent formation. On the other hand, as I said My field of interest is molecular that, as J. Larralde would say, it is not before, the Herschel observatory astrophysics. The observation of possible even to write a history about —of which I am one of the mission molecules is the only way to any of those topics. scientists— is already flying and their determine the physical conditions of instruments are providing a the gas and its chemical evolution. How did it influence your complementary view to ALMA in the The study of star formation must be professional career? Have you far infrared. done in parallel with the study of the continued in that line of work? Has it surrounding protoplanetary disks. The opened new perspectives or later did Do you have any anecdote related detection of exoplanets is a fascinating you dedicate yourself to other topics? to this paper’s gestation and area and in a few years we will have a Both! I have continued in this research publication that you think is worth fairly wide census, including earth-like line, getting more interested in telling? planets. The study of the evolution of protoplanetary disks, in particular in Indeed. Mi interest in the Trifid the gas from the diffuse clouds up to the chemistry of the gas that undergoes started during a popular talk in a its accretion onto the forming —gas the extreme conditions we find in these school in Madrid. I was talking about 67 Astronomy made in Spain
the interstellar medium and the entering the ionized area of the on the Trifid using data from ISO and physical processes occurring when a region. I stared silently for about a other observatories. massive star forms and completely minute... I had worked before on modifies its surroundings. I chose for molecular jets from low-mass stars. that an image of the Trifid. In the When I finished my talk I browse the INDUCED MASSIVE STAR FORMATION IN THE TRIFID projection on the screen the image literature. There were many images of NEBULA? was inverted. In explaining the image the region, and the jet was apparent in J. CERNICHARO, B. LEFLOCH, P. COX, D. CESARSKY I realized of something that I had many of them, but nobody said AND SIX CO-AUTHORS never seen before, and not only me, anything about it. The first paper in 1998, SCIENCE, 282, 462 but all the astronomers that had been Science is, in part, devoted to that jet, studying this object for more than half that has been named HH399 WINDOWS THROUGH THE DUSTY DISKS SURROUNDING a century!. There was a cometary afterwards. It is the first totally ionized THE YOUNGEST LOW-MASS PROTOSTELLAR OBJECTS globule, an object under the jet emerging from a low-mas star J. CERNICHARO, A. NORIEGA-CRESPO, D. CESARSKY, ultraviolet radiation field from the star formed recently. Since then, several B. LEFLOCH AND FOUR CO-AUTHORS that illuminates the nebula; a sort of more cases have been found and we 2000, SCIENCE, 288, 649 jet was expelled from the globule, have published more than ten papers
68 Eduardo Martín Guerrero de Escalante Instituto de Astrofísica de Canarias (Tenerife)
What was the problem you had objects. The first binary system Which are the main problems to face? with an L-type companion was in this area of Astrophysics The problem we had to tackle was discovered. and what are the expected the characterisation of the properties discoveries in the coming years? of the first brown dwarfs of spectral Since the paper was published, Among the many problems in this type L in the solar neighbourhood. have there been significant advances hot topic, I would highlight the Brown dwarfs are objects which lie in this specific area? determination of the mass-luminosity in what we call the “substellar limit”, Yes, dozens of very low mass binaries relation for brown dwarfs, the that is, they are not stars because have been detected, and even some discovery of very low-mass eclipsing they do not fuse hydrogen as in the planetary mass objects. The dynamic binaries and planets orbiting around Sun. masses of several brown dwarfs have brown dwarfs. been measured. The general What was the solution multiplicity properties of brown Did it influence your professional to this problem and the contribution dwarfs, like the frequency of binaries, career? Have you continued this paper made to the area semi-major axis distribution and the in that line of work? Has it opened of expertise in which it is framed? mass ratio, have been studied. These new perspectives or later did you For the first time it was possible results have been used to restrict the dedicate yourself to other to obtain images of a binary brown validity of formation scenarios for topics? dwarf using the Hubble Space very low mass objects. Yes, it did. I have continued Telescope. It was proven that it is with this line of work, although possible to detect the companions lately I have been dedicated to other of brown dwarfs with sufficient topics. sensitivity to detect planetary mass 69 Astronomy made in Spain
Do you have any anecdote related was observed that curiously was also to this paper’s gestation and a binary (although that was publication that you think is worth discovered seven years later) but we telling? could not resolve it because its orbit The data were obtained using the was eccentric. director’s discretionary time on the Hubble Space Telescope. When I saw the first double brown dwarf, the A SEARCH FOR COMPANIONS TO NEARBY BROWN first thing I thought was that the DWARFS: THE BINARY DENIS-P J1228.2-1547 telescope had moved or that I was E.L. MARTÍN, W. BRANDNER AND G. BASRI Figure 1. Comparison of some properties (size, seeing double. Another brown dwarf 1999, SCIENCE, 283, 1718 temperature and colours) among the Sun, a white dwarf M (Gliese 229 A), two brown dwarfs (Teide 1 and Gliese 229 B) and Jupiter. Brown dwarfs bridge the mass gap between stars and planets. A substellar object is considered a brown dwarf if its mass is between 0.013 solar masses (13 times the mass of Jupiter) and 0.070 solar masses.
70 Alberto J. Castro Tirado Instituto de Astrofísica de Andalucía (CSIC, Granada)
What was the problem you had What was the solution to this we also found two important results: to face? problem and the contribution this 1) the evidence of a change in the In 1999, the nature and many paper made to the area of expertise slope of the light curve in the optical, physical properties of cosmic in which it is framed? which we interpreted as the strongest gamma-ray bursts (GRBs) were still A large amount of data was obtained evidence for a collimated jet of unknown and when the intense burst over all the electromagnetic spectrum material with an aperture angle occurred on January 23 (visible for and with different observational of a few degrees; and 2) a limit on a few seconds with a simple pair of techniques (especially in the optical: the degree of linear polarization of 8% binoculars) we tried to collect as photometry, spectroscopy and in the optical. much data as possible to give the polarimetry). Three Letters in Science most satisfactory explanation for and one Article in Nature were Since the paper was published, have the observed phenomenon. published; I was the first author of there been significant advances We should not forget that the one of the Letters in Science and co- in this specific area? nature of GRBs only started to be author of the others (the three letters Yes, many. In the field of GRBs there clarified some thirty years after their were published consecutively in the have been many discoveries to date, discovery when, in 1997, the X-ray same issue). both in the exploration of long- emission that follows the initial The cosmic cataclysm occurred 9 duration gamma-ray bursts higher energy emission (gamma rays) billion light-years away, implying that (associated with the gravitational for a few hours (or days in some it was the most luminous cosmic collapse of very massive stars that cases) was detected (the so-called object in the observed universe to date give rise to the birth of new black afterglow). (night would have turned into day if holes, confirmed in 2003) and in the it would have been in our Galaxy). In short duration GRB population our work that was published in Science (with the discovery of the first 71 Astronomy made in Spain
Figure 2. Images obtained with the Hubble Space Telescope of the optical afterglow emission from GRB 990123 superimposed to the host galaxy (at least two galaxies appear to be interacting 9,000 million light-years away) 23 (left) and 59 (bottom left) days after the burst. Note how in the last image (bottom right), taken a year later, all the residual light from the GRB has disappeared. Courtesy of Fruchter et al. (1999).
Figure 1. An artist’s concept of the gravitational collapse of a very massive star originating the cosmic gamma-ray burst. Its wavefront reached the “electronic eyes” of the scientific satellites on January 23, 1999, after travelling in space for some 9,000 million years. Courtesy: NASA/Zhang & Woosley.
examples in 2005.) In fact, since observed emission after the initial short-duration GRBs, such that 1997, there must be some thirty gamma-ray burst, clearly presents existing examples would be papers published in both journals some serious limitations in explaining short class II GRBs, while class I short metioned above for all the groups the detailed light curves which are GRBs would be practically unknown that are working in this field. being obtained by multiwavelength because of the small number of data observations, such as those obtained available. Among the many Which are the main problems in this with the SWIFT satellite. Also the discoveries to be made are: 1) the area of Astrophysics and what are existence of a population of detection of GRBs further away than the expected discoveries intermediate-duration GRBs with the furthest known objects, which in the coming years? a different physical nature is under will be related to the first generation The theoretical model, the so-called debate. Even more uncertain, is a of stars created in the Universe; 2) “Fireball model”, used to explain the possible dichotomy in the class of the detection of gravitational waves 72 Spanish Astronomical Society
“Break” contributed to maintain this line of time work as the most productive of all Relativistic the others in which I am involved, Jet opening effects angle to the point that in parallel over the last 15 years I have guided the Jet technological developments in Gamma-ray burst (GRB) Earth robotic astronomy using central engine r-100 r-50 r-10 ultrasensitive cameras for r-2 continuously searching variable objects in the night sky.
Observed flux Do you have any anecdote related to this paper’s gestation and publication that you think is worth telling? Time Yes, regarding the typical race when two scientific teams have Figure 3. Theoretical interpretation of our coming from the coalescence of independent data that can yield the observations within a relativistic “fireball model”. The neutron star binary systems. same big impact discovery. In this change in the slope is observed during the so-called specific case, the team led by “break” time, when the collimated emission is Did it influence your professional Professor S. Kulkarni (Caltech, USA) accelerating (the Lorentz factor decreases) and therefore, the aperture angle of the emission cone career? Have you continued in that and the one led by me (I was then increases exceeding the emission cone that we see from line of work? Has it opened new working under a contract limited to the Earth due to the relativistic effect. This results in perspectives or later did you a specific project at INTA and worked an “apparent” loss of photons as an observational fact. dedicate yourself to other topics? physically at IAA-CSIC). Kulkarni Adapted from Piran (1999). Undoubtedly, these and other et al. sent their paper to Nature. We publications I have written on the sent ours to Science. There is no same field (two as a first author doubt that both journals knew about in Science, one as a first author the paper that had been sent to its in Nature, and eight more as a rival on the same object (GRB co-author in both journals) have 990123). The two months between 73 Astronomy made in Spain
the phenomenon occurrence and the who was going to be the leader of the as the second co-applicant of the new publication of the results were mentioned publication in Nature. time request. But this time without frenetic, but it was worth the stress. The day following the journalist’s my consent! As I was the discoverer The Spanish team (and Science) won phone call, I phoned the head office of the object in question and the the round to the California’s of the European Space Observatory author of several papers on the powerful team (and Nature) by seven (ESO) in Munich —the data used subject, my name was used without days and therefore Nature had to for the paper published in Nature permission in order to obtain time advance the press release with the had been obtained with one of the to observe the object with the VLT, announcement by a week! It was VLT telescopes (ESO, Chile)— which turned out to be a probably, the first time in its long and I asked them for a copy of the fundamental part of the paper to be history that Nature had to change its observing time request made by published in Nature. Logically, policy in this sense… the first author of the paper in I immediately thought of contacting question, with the “false” excuse that ESO and Nature but, in the end, ADDENDUM: Not everyone follows I did not keep a copy of it (obviously I decided to leave things as they the same game rules they assumed that I was were. Of course, then I contacted Some years ago, I received a call from a co-applicant). the first author of the paper in a journalist from Nature asking my As I had mentioned above, a year Nature (and ex-friend since then) opinion on a discovery that was before we had worked together on and immediately rejected any future going to be published in a paper the same object using data from collaboration with him. And it is like several weeks later, of which I was ESO, that we were able to obtain this even now… not a co-author. He was calling me because we had previously sent Unfortunately, not everybody because I had discovered the object a request for observing time which (neither in science nor in life) follows in question in 1992 and this, I had signed as a co-author (at that the same game rules. as it turned out, was going to be time Spain was a few years ahead announced as the most massive black before becoming a full member.) hole in our Galaxy (to date). Of After a few minutes and following DECAY OF THE GRB 990123 OPTICAL AFTERGLOW: course, I praised the work done and my request, I received by fax the full IMPLICATIONS FOR THE FIREBALL MODEL the importance of the result. proposal that had been sent, with A.J. CASTRO-TIRADO, M.R. ZAPATERO-OSORIO, N. However, I had my suspicions, a year reference number 65.H-0422. CAON, L.M. CAIROS AND 48 CO-AUTHORS before I had collaborated with the Unfortunately my suspicions were 1999, SCIENCE, 283, 2069 scientist (and friend at that time) confirmed. My name appeared again 74 Pere Planesas Bigas European Southern Observatory (Santiago, Chile)
What was the problem you had Our methods proved for the first potentially producing several images to face? time the viability of those studies. of the background object. Moreover, The problem was to determine the when acting on an extended galaxy, quantity, distribution and kinematics What was the solution to this gravitational lensing increases its of the molecular gas in galaxies problem and the contribution this apparent size (Figure 2). Thanks located at cosmological distances. paper made to the area of expertise to this effect, the brightness of the Stars are born from this gas, that is in which it is framed? molecular gas emission was amplified why its study is essential to know the The solution was to observe a very by the gravitational lens allowing us star formation history and efficiency particular galaxy, in the sense that to detect it and, acting as a “cosmic in very distant galaxies, which are there is another very massive galaxy magnifying glass”, increased its therefore very young. At that time in the line of sight between it and us apparent size and, therefore, we were (1999), it had not been possible to that acts as a gravitational lens able to measure its distribution and detect molecular gas in any galaxies (Figure 1). This gravitational lens was kinematics. The latter had not so far at redshifts between 1 and 2, in other known for its effect on the light been possible for the few galaxies words, when the Universe was emitted by the powerful quasar that located at even larger distances that between 1/4 and 1/3 of its present resides within the distant background had been detected at that time. age. The observational problem was galaxy. This effect, explained by the weakness of the emission and the Einstein’s general relativity theory, Since the paper was published, have small angular size in which the the intervening mass along the line- there been significant advances molecular gas is distributed due to of-sight causes the radiation emitted in this specific area? the large distance to these galaxies, by a background or distant quasar Since then, molecular gas has been which made it impossible to detect to deviate from its normal path, detected in three other galaxies them with the telescopes of the time. amplifying its brightness and located at the same redshift range. 75 Astronomy made in Spain
Most molecular gas detections in especially complicated in the case galaxies at these distances, or even of molecular gas measurements taken further, have been possible thanks with high-frequency radio waves. to the presence of an intervening We can only obtain very detailed gravitational lens, very often initially information in those cases where unknown. However, the galaxy we a gravitational lens increases its size. detect is similar to the Milky Way, However, this technique has given while the other galaxies are less results in only very few occasions; normal, they are richer in molecular one of them is the “twin quasar”. Figure 1. Explanatory sketch of the gravitational lensing effect. As the observer and both galaxies are gas. The originality of our project For it to be really effective, a radio aligned, if the intervening galaxy (or galaxy cluster) is was to choose a case in which we interferometer capable of measuring massive enough the observer can even see two or more knew about the existence and details much smaller than those images of the distant galaxy. In our case this galaxy characteristics of a gravitational lens measured with present harboured a quasar. lying between us and the galaxy that interferometers is needed. Such harbours the quasar. In fact, the an interferometer, called ALMA, is chosen quasar was the one where the currently being built in the Atacama gravitational lensing phenomenon desert at 5000 meters altitude, from was first discovered (20 years before, where these very difficult in 1979) and it is known as the “twin observations will be routine in quasar”, since its optical image a few years time. At present, I am consists of two bright spots participating in the construction (Figure 3). of this observatory.
Which are the main problems in Did it influence your professional Figure 2. An artist’s concept showing the distortion of this area of Astrophysics and what career? Have you continued in that a distant galaxy produced by a gravitational lens. The are the expected discoveries in the line of work? Has it opened new quasar that resides inside this galaxy produces two coming years? perspectives or later did you plasma jets that emit radio waves. The lens duplicates One of the main difficulties in dedicate yourself to other topics? and distorts the image. This is not appreciated in Figure 3, as a quasar is a point-like source, but it is determining the characteristics of A large amount of my scientific appreciated in the case of a galaxy, an extended source. galaxies in the early universe is that research during the years previous we do not know their size. This is to the publication of this paper was 76 Spanish Astronomical Society
related to the study of luminous and journals, based on the evaluation ultraluminous infrared galaxies. of one or more scientists who decide These galaxies have bursts of star if the paper is suitable for publication formation that give rise to hundreds in the journal. Such evaluation, of new stars per year, at a rate a which always attempts to be hundred times faster than in our objective, sometimes has editorial Milky Way. biases, as it happened to us when That paper was my first foray into Nature rejected our paper, while the the study of the distant universe, other one, Science, accepted it where other galaxies with high rates immediately. of star formation are also detected. After this paper’s publication, Their study can be based on the I could see the great interest closer ultraluminous galaxies that generated (the news was published in Figure 3. Optical image of the “twin quasar” QSO I previously studied. Recently, I have the newspaper El País and in several 0957+561 showing two point-like images formed by participated in the characterisation scientific vulgarization magazines, the the intervening gravitational lens and a faint image of of dense molecular gas in a galaxy at Madrid Planetarium invited me for the galaxy which originates the phenomenon. This is a redshift of 3.9 (when the Universe a conference, etc.); the question that the first case of gravitational lensing discovered and one was only 10% of its present age). aroused the most interest among the with one of the largest image separations known (6''). Courtesy of the CASTLES project: This galaxy harbours one of the most people who asked me about the http://www.cfa.harvard.edu/castles/ luminous quasars in the Universe and subject was the use of gravitational it also experiences amplification due lenses as an enhancement of the to the gravitational lensing telescope’s capability. phenomenon.
Do you have any anecdote related GAS-RICH GALAXY PAIR UNVEILED IN THE LENSED to this paper’s gestation and QUASAR 0957+561 publication that you think is worth P. P LANESAS, J. MARTÍN PINTADO, R. NERI telling? AND L. COLINA One anecdote previous to the 1999, SCIENCE, 286, 2493 publication of the paper is related to the editing process followed by these 77
Héctor Socas Navarro Instituto de Astrofísica de Canarias (Tenerife)
What was the problem you had What was the solution to this technique, developed and tested to face? problem and the contribution during my thesis, gave us the The chromosphere (upper layers this paper made to the area of possibility of relating the of the atmosphere) above sunspots expertise in which it is framed? observations with the changes taking exhibits a very dynamical behaviour, We approached the problem in two place in the solar atmosphere. including sudden brightenings with ways, using both observational and During the course of our research a period of about 3 minutes. These analytical advances. On the one we had a surprise, since the form brightenings, called umbral flashes, hand, we used a new instrumental set of the polarization profiles changed were discovered observationally in the for the spectropolarimetric during the umbral flashes and became sixties and even now little is known observations in the near infrared, strongly asymmetric. These profiles, about their physical nature and origin. specifically in a spectral range where which we named as “anomalous”, The study of these phenomena is the chromosphere can be observed. were too asymmetric very complicated because they take Polarimetry allows us to study the to be explained with magnetic field place in highly magnetized magnetic field and its relation to the or velocity gradients. The environments (sunspots have a observed phenomena, hence its interpretation of these observations magnetic nature) and because in the importance in this scenario. This led us to the conclusion that those chromosphere the usual diagnostic type of observations had not been umbral flashes worked as a group techniques are not normally possible before our work. of geysers that ejected jets of hot applicable. Also, due to the dynamic The second method was to use material to the top layers of the character of the umbral flashes, follow a new diagnostic technique which atmosphere. These jets, which reach up data is required on very short allowed us to make inversions of lines velocities of about 15 km/s, have timescales and periods to study its formed outside the local a very small horizontal extension nature. thermodynamical equilibrium. This (smaller than 1000 km) and go 79 Astronomy made in Spain
through a relatively calm and much data do not allow the phenomenon colder atmosphere. dynamics to be studied but they do confirm the prediction that we had Since the paper was published, made in our work. have there been significant advances in this specific area? Which are the main problems 30 In general, there has been little in this area of Astrophysics 25 advance due to the difficulties and what are the expected 20 mentioned above, both in making discoveries in the coming years?
15 suitable observations (polarimetry The chromospheres of the Sun and Mm in chromospheric lines) and in the the stars have incomprehensibly high 10 development of the analysis temperatures, and this is one of the 5 techniques (combination of inversion major problems in stellar physics 0 algorithms with radiative transport today. We think that wave 0 5 10 15 20 25 outside the local thermodynamic propagation in small vertical Mm equilibrium). Perhaps the most magnetic elements and the existence Figure 1. Image of a sunspot with magnetic field lines significant advance is the one of small-scale reconnection that pierce the chromospheric region above the presented in a recent publication phenomena are the key to this penumbra. The units in the axes are millions using high-resolution imaging enigma. It is speculated that the of meters. observations from the Hinode umbral flashes could be a large-scale satellite (Socas-Navarro, McIntosh, version of what could be happening Centeno, de Wijn and Lites 2008). in continuously all over the Sun to Unfortunately, Hinode does not heat the chromosphere. At present, allow polarimetric measurements we do not have appropriate tools to of the chromosphere to be made, investigate these processes, as they but the quality of its high spatial take place at very small spatial scales resolution images allows to directly and require the observation of see that there is really a mix of hot chromospheric lines. In the next and cold material when the umbral decade, with the construction of flashes occur. Since spectroscopy and ATST (Advanced Technology Solar polarimetry are not possible, Hinode Telescope) and EST (European Solar 80 Spanish Astronomical Society
Telescope), we hope to be able to make these observations. The 50 35 development of computational resources will also be important, as 30 1D (one dimension) models that we use in our research will no longer be 40 suitable outside sunspots. It will be 25 necessary to make inversions with 0 5 10 15 20 radiative transport in 3D (three
Arc-seconds 30 dimensions) outside the 35 thermodynamic equilibrium, and this will require supercomputers, to 30 which it is very difficult to have 20 access to. 25 Did it influence your professional 0 5 10 15 20 0 5 10 15 20 career? Have you continued in that Arc-seconds Arc-seconds line of work? Has it opened new perspectives or later did you Figure 2. In this sunspot we can see the darker and colder central region (umbra), and the dark and bright dedicate yourself to other topics? penumbral filaments. On the right, the contour plots that limit similar magnetic field values. Generally I have continued working in the field of the chromospheric dynamics but I have not been particularly centred in umbral flashes. Since the publication of this paper, I have published two more (Centeno, Socas-Navarro, Collados and Trujillo Bueno, 2004 and the mentioned Socas-Navarro, McIntosh, Centeno et al. 2008) where other evidence confirming the predictions 81 Astronomy made in Spain
of the original paper were presented. Observatorio del Teide, which was of the story is that the most I hope that with the development of already considered obsolete and was sophisticated is not always the best. new solar telescopes it will be about to be closed. In fact, I think Flexibility is also important because possible to make the observations we that our observations were some in science it is impossible to foresee need to move forward in this field. of the last made there. It was a very all the possible future needs. simple instrument and, precisely, Do you have any anecdote related because of that simplicity we were to this paper’s gestation and able to reconfigure it and build the ANOMALOUS POLARIZATION PROFILES IN SUNSPOTS: publication that you think is worth setting we needed to collect our data. POSSIBLE ORIGIN OF UMBRAL FLASHES telling? At that time, it was almost H. SOCAS NAVARRO, J. TRUJILLO BUENO The data were obtained with the impossible to carry out our study AND B. RUIZ COBO Gregory Telescope at the with any other telescope. The moral 2000, SCIENCE, 288, 1398
82 Vicent Quilis Quilis Departament d’Astronomia i Astrofísica Universitat de València
What was the problem you had galaxies. These observations have third hypothesis suggested that galaxy to face? given rise to many hypotheses on the interactions with cluster The study of the morphological nature of this effect and more than environments (the intracluster transformation of galaxies is one a thousand papers have been written medium) could cause the of the most fascinating topics in on the subject but with no clear aforementioned metamorphosis. astrophysics, and it has crucial conclusions. In the year 2000, we Previous studies based on very high implications in the theoretical model still did not understand the reasons resolution N-body simulations had that would allow us to understand behind the large differences between dismissed the first two hypotheses, the formation of structures that build cluster galaxy populations according while some preliminary attempts, up the Universe. In particular, the to their age. with inappropriate techniques, had so-called Butcher-Oemeler effect, failed to adequately describe the which implies that galaxies in nearby What was the solution to this interactions with the environment. clusters are very different from problem and the contribution Our idea was to study, with the galaxies in distant clusters, has been this paper made to the area of latest generation computational known for a long time. With the expertise in which it is framed? techniques, the interaction between arrival of the Hubble Space There were three main hypotheses spiral galaxies and their environment. Telescope, we could observe the to explain the origin of S0 galaxies in In order to do this, we used the important difference between galaxy clusters. The first one pointed to the cosmological code I developed during populations in nearby clusters, which effects of tidal forces experienced by my PhD thesis, which was able to are dominated by small spheroidal spiral galaxies when interacting with precisely describe fundamental galaxies (S0) without outstanding the structure surrounding them. The phenomena associated with the features, whereas distant cluster second theory referred to the effects gaseous components of cosmological populations are dominated by spiral of galaxy mergers. And, finally, the structures, such as shockwaves 83 Astronomy made in Spain
64 Kpc In order to make these simulations, we used the most powerful computer of that time in the United Kingdom and it took three months of intensive
t=0.0 t=5.2 t=9.8 calculations that generated a huge amount of data.
Since the paper was published, t=14.9 t=14.9 t=31.0 have there been significant advances in this specific area? Figure 2. Synthetic radio map of a spiral galaxy Since the publication of this paper travelling through the intracluster medium. Contour lines represent the emission associated with the gas, there have been important advances t=47.5 t=67.0 t=75.0 while the grey-scale shows the density of that gas. in this field. Several groups have made The image shows the compressed contour lines -0.9 0.1 1.1 2.1 3.1 similar simulations, with different log ( ) in the direction of motion and the gas tails behind techniques and higher numerical the galaxy. This image can be compared directly with resolutions, confirming the results observations. Figure 1. Temporal evolution of the gaseous disk of a presented in our paper. It has also spiral galaxy (viewed edge-on) when interacting with been possible to study the interaction the intracluster medium. After a hundred million phenomena with the environment in years the galaxy has lost almost all its gas and has and the formation of instabilities and different ranges of the electromagnetic run out of fuel for star formation. Like the gas, the other galaxy components (not shown in the figure) turbulence, to simulate the effects spectrum, thanks to a new generation have also suffered important changes, so that the end suffered by a typical spiral galaxy when of observations that have also of the process is a system with the typical morphology orbiting in the intracluster medium. confirmed our predictions. of a S0 Galaxy. The right description of this complex physical scenario permitted Which are the main problems in this us to conclude that the interaction area of Astrophysics and what are with the intracluster medium the expected discoveries in the transformed, in time scales of coming years? hundreds of millions of years, spiral The creation of a theoretical- galaxies into spheroidal galaxies (S0) observational framework, which will with very low star formation rates. help us to understand the formation 84 Spanish Astronomical Society
and evolution process of galaxies, career, as it has become a classical a shocking title but we did not agree. is undoubtedly one of the main reference in this field. In fact, the One day, taking a coffee, we were objectives of modern astrophysics. interaction mechanism with joking about making a version of that On a galactic scale, there is an overlap the intracluster medium is now the great classic film: Gone with the between the influence of the accepted explanation of the origin wind. After some minutes of cosmological evolution of the of S0 galaxies in clusters, both by hesitation, it was clear that it was Universe as a whole, and galactic theoretical and observational going to be the definitive title of our and stellar astrophysics. Therefore, the colleagues. paper. search of a global paradigm that Now I am starting to work on this Another curiousity was the describes the formation of the large- topic again using new generations of disparity between the reports of the scale structure and the star formation cosmological codes. The basic idea is referees. One of them was extremely process in the Universe must entail to form galaxy clusters from enthusiastic and was urging us to the understanding of galaxies. In this cosmological initial conditions but publish the paper, while the other sense, research aimed towards with enough resolution as to describe one, although favourable, had certain disentangling all aspects of galaxy the galaxies that populate those doubts and was asking for some evolution, and in particular its clusters. In this way, we will be able additional material. Finally, morphological transformations, to follow the evolution of those the latter referee was satisfied with is fundamental for the description virtual galaxies and to study all the the additional material we provided of the Universe. phases and transformations occurred but it could not appear in the during their lifetime. magazine because of a space How did it influence your limitation. professional career? Have you Do you have any anecdote related continued in that line of work? Has it to this paper’s gestation and opened new perspectives or later did publication that you think is worth GONE WITH THE WIND: THE ORIGIN OF THE S0 you dedicate yourself to other topics? telling? GALAXIES IN CLUSTERS The publication of this paper has Perhaps the most curious thing was V. Q UILIS, B. MOORE AND R.G. BOWER been important in my professional the choice of the title. We wanted 2000, SCIENCE, 288, 1617
85
Josep María Paredes Poy Departament d’Astronomia i Meteorologia Universitat de Barcelona
What was the problem you had These microquasars had been made it possible to select a short list to face? discovered as a result of some of candidates. In the nineties the existence of a new eruptive episodes detected by X-ray Subsequent observations with the type of stellar object in our Galaxy observatories in terrestrial orbit. We VLA (Very Large Array) enabled was established: which are X-ray decided to look for new microquasars detailed studies of the candidates, binaries with relativistic jets, also but without having to wait for an and in particular, to improve the known as microquasars. In these eruption that alerted us. position of one of them, especially systems, an ordinary star orbits interesting, LS 5039. To be sure that around a neutron star or a black What was the solution to this it was a microquasar we had to prove hole, which captures (accretes) mass problem and the contribution that it had jets and, for that, we used from the bright companion star and this paper made to the area of the VLBA (Very Long Baseline forms an accretion disk. A fraction expertise in which it is framed? Array) radio interferometer. As we of the mass accreted is ejected at To identify potential microquasar expected, the analysis of the relativistic velocities in a direction candidates, we used different observations showed an elongated perpendicular to the accretion disk, catalogues in the optical, radio and and asymmetric structure. It was creating the jets that characterize X-rays that contain the position and what we were looking for. In microquasars. energy emitted by the catalogued addition, the microquasar position Just a few more than a dozen sources in the different wavelengths. coincided with an unknown very microquasars were known and it was With the aid of computers, and high-energy gamma-ray emission important to expand the sample to taking into account relevant source. We proposed that the new characterise the observed properties of microquasars, we microquasar, LS 5039, was also a phenomenology with a broader carried out a detailed inspection of gamma-ray emitter. This discovery statistical base. those astronomical databases, which represented the first observational 87 Astronomy made in Spain
evidence that microquasars can also Which are the main problems in this be high-energy gamma sources, and area of Astrophysics and what are that an important part of the the expected discoveries in the gamma-ray sources not yet identified coming years? could be compact extragalactic One of the major problems, which objects connected with microquasars. affects both microquasars and quasars, is to know the formation Since the paper was published, have mechanism of relativistic jets and the there been significant advances processes of matter accretion onto in this specific area? the black hole. In the next years, the There have been amazing advances. Fermi gamma-ray satellite, launched Figure 1. Artist’s concept of a binary star system where In 2005, five years after proposing in June 2008 by NASA, is expected a black hole captures matter from its companion and that microquasars are also gamma-ray to detect a large number of sources, ejects part of it in the form of relativistic jets. Credits: emitters, the Cherenkov HESS and microquasars are probably a ESA, NASA and Félix Mirabel (CEA and telescope detected LS 5039 in very fraction of them. This will allow us CONICET). high energy gamma rays, confirming to study the energetic mechanisms our discovery and extending the associated with accretion/ejection emission energy range of processes. microquasars. In 2006, the Cherenkov MAGIC telescope located Did it influence your professional on the island of La Palma, detected career? Have you continued in that variable emission from the line of work? Has it opened new microquasar LSI+61303 and in the perspectives or later did you year 2007 it also detected fast dedicate yourself to other topics? variability emission in the Yes, it influenced my career. This microquasar Cygnus X-1, which is discovery made it easier for me to get the best candidate for harbouring a involved in high-energy Astrophysics. black hole. We have broadened the issues we were 88 Spanish Astronomical Society
working on. One of them is related to Do you have any anecdote related sources that emit gamma-rays and are to this paper’s gestation and not identified due to the poor angular publication that you think is worth resolution of the observation instrument. telling? We explored the area around the At the end of 1999, we received the gamma ray source with different data from our observations with the instruments (radio telescopes, satellites VLBA. The analysis of these data had with X-ray detectors, optical to tell us whether we had discovered telescopes, the Cherenkov telescope) a new microquasar or not. As we to identify what object (microquasar, were very anxious to know if the pulsar, galaxy’s active nucleus, etc.) source, LS 5039, showed jets we is responsible for the gamma ray decided to work during the whole emission. We also developed Christmas holidays. And we received theoretical models consistent with the our present! observational data and that make it Figure 2. Composition showing the Very Large possible to reasonably explain all the Array (VLA), an interferometer located in New Mexico, and the high resolution radio frequency associated phenomenology. DISCOVERY OF A HIGH-ENERGY GAMMA-RAY-EMITTING map of the microquasar LS 5039 obtained with PERSISTENT MICROQUASAR the VLA and the VLBA at 6-cm wavelength. J.M. PAREDES, J. MARTÍ, M. RIBÓ AND M. MASSI The emission is more intense in the central 2000, SCIENCE, 288, 2340 region (nucleus, in red), while the lobules on the left and right sides (jets) are fainter.
89
José Luis Ortiz Moreno Instituto de Astrofísica de Andalucía (CSIC, Granada)
What was the problem you What was the solution to this Leonid meteor shower of 1999 would had to face? problem and the contribution offer an excellent opportunity to I wanted to know the amount this paper made to the area of detect, beyond any doubt, impact of matter that there is in the expertise in which it is framed? flashes against the Moon. Finally, trans-neptunian belt (the zone I found a way to determine the this was achieved in November 1999, beyond Neptune, where Pluto and amount of very volatile matter in the and in the year 2000 we published other bodies lie). I believed that there vicinity of the Earth by pointing our our results in the journal Nature. could be a large amount of it in the telescopes towards the night side form of small frozen bodies, with of the Moon that is visible from the Since the paper was published, very volatile ices, and sizes between Earth and searching for flashes have there been significant advances centimetres and meters. Some of of light produced each time a big in this specific area? these bodies could reach Jupiter and enough object impacted against that Yes, soon after we were able to even reach the Earth or its vicinity part of the Moon. We knew that determine the fraction of impact (the Moon) but due to their large when a body collides with another energy that is emitted in the form volatility, if they were on a course body at enormous speeds, the of visible light in the collision to collide with the Earth most likely impacting body vaporizes (it processes with more precision than they would disintegrate very quickly disintegrates in a sort of gas) and in our Nature paper. And some time in the atmosphere, and therefore they emits light during the almost later, in 2002, we made the first would not produce the meteors instantaneous process, therefore detection of sporadic impacts to which we are used. making it possible to see impacts (impacts produced by bodies of of very volatile matter. In 1998 we unknown origin, not associated with tested the technique, but without meteor showers, which are showers of success, and proposed that the material of known comets). Sporadic 91 Astronomy made in Spain
impacts were the ones we were Did it influence your professional looking for from the beginning career? Have you continued in that and we were able to determine the line of work? Has it opened new number of volatile material impacts perspectives or later did you against the Earth according to their dedicate yourself to other topics? energy. Our preliminary conclusions I guess that it did influence my indicate that three times more career because this type of material than previously expected contributions are very positively arrives and most of it is volatile. evaluated by reviewing panels, and Following the success of our helps in the way that the committees Figure 1. Synthetic image of the Moon where five real pioneering work, NASA established that finance research in Spain are, images of impact flashes detected in November 1999 a specific program to make the same sometimes, more prone to grant have been superimposed. The brightness of the dark measurements we did, starting in money for projects. After the paper side of the Moon has been artificially enhanced. 2005. in Nature, I obtained my own funding to do this research for the Which are the main problems first time. Perhaps it was by chance, in this area of Astrophysics perhaps not.... Until that time the and what are the expected work had been done without any discoveries in the coming years? specific funding, using other This is a very broad and new field, financial resources and funding and therefore there are many things means where there were none. Even to explain and study in depth. the labour, fundamental for all Perhaps one of the most important scientific research, was given by problems is to determine the precise amateur astronomers who did not place from where the most volatile even belong to a research centre. I material we see impacting against the continued working on the topic but Moon originates. not as my primary scientific activity because it required much more effort than I could afford with the human and economic resources I had. 92 Spanish Astronomical Society
Do you have any anecdote related time. It was thought that a cosmic ray commonly associated with aliens and to this paper’s gestation and hit his eyeball and I knew this occultism and called “lunar transient publication that you think is worth “official” version, but Jack asked me phenomena”, have been explained telling? if he could have witnessed an impact as impact phenomena of After the publication in Nature, of a body on the Moon. Thanks to interplanetary material against the the North American astronaut of the the data he provided me, I reached the surface of the Moon and nothing Apollo XVII mission and former conclusion that he had probably seen related to aliens. United States senator from New an impact from a Geminid shower Mexico, Harrison Schmitt, contacted particle. He was very happy to know me to tell me something that that what he had seen was real and OPTICAL DETECTION OF METEOROIDAL IMPACTS ON happened while he was piloting the not a hallucination, as some people THE MOON Lunar Module in December 1971. wanted him to believe. Of course, it J.L. ORTIZ, P.V. SADA, L.R. BELLOT RUBIO, F.J. Harrison Schmitt, better known as had nothing to do with aliens. ACEITUNO, J. ACEITUNO, P.J. GUTIÉRREZ AND U. THIELE Jack Schmitt, saw a large flash, but the Many other luminous phenomena 2000, NATURE, 405, 921 event remained unexplained for a long that occurred on the Moon,
93
José Luis Gómez Fernández Instituto de Astrofísica de Andalucía (CSIC, Granada)
What was the problem you the jet and a cloud in the of these have provided a significant had to face? intermediate region between the advance in the understanding of Thanks to the start of the broad- and narrow-line region ((BLR relativistic jets. commissioning of the Very Long and NLR, respectively). Baseline Array (VLBA) it was This made it possible to determine Which are the main problems possible to make a detailed follow up the important role of the in this area of Astrophysics (with a high spatial and temporal surrounding medium in the study of and what are the expected resolution) of a relativistic jet in an jets in AGN, and on the other hand, discoveries in the coming years? active galactic nucleus (AGN). the important contribution of the jet What it is still unknown are the The study, carried out in the radio itself in the evolution of the galaxy processes of jet formation, galaxy 3C120, showed an unusual that harbours it (something that is acceleration and collimation, variation in the hydrodynamics and very topical in cosmological especially important for the study non thermal emission, consisting of a simulations today). of AGN, GRBs and microquasars. sudden increase in the emission A second paper in Nature, where together with a rotation of the Since the paper was published, I appear as a co-author, followed this polarization angle. have there been significant advances line of work. In the next years a in this specific area? significant advance in those topics What was the solution to this Yes, similar studies on other is expected, mostly thanks to the problem and the contribution relativistic jets have continued FERMI satellite and to the Japanese this paper made to the area of to be done, together with numerical VSOP-2 mission. expertise in which it is framed? simulations of hydrodynamics and These observations were explained as emission, and the role of feedback being due to the interaction between of the jet in the galactic evolution, all 95 Astronomy made in Spain
How did it influence your professional career? Have you continued in that line of work? Has it opened new perspectives or later did you dedicate yourself to other topics? I have continued my research in this topic.
Do you have any anecdote related Figure 2. Real images of the radio galaxy 3C 120, to this paper’s gestation and over an artist’s concept, showing the temporal publication that you think is worth evolution of the jet. telling? I do not remember anything special. Perhaps the most surprising thing was the great stir caused by the media. I think that sometimes journalists are so afraid of not echoing something correctly that Figure 1. Artist’s concept of an active galactic nucleus they can create a big snowball. It was (AGN) with two relativistic jets perpendicular to the also a time when being Spanish and disks. publishing in Science or Nature was a big asset. Now I think that is not the case (which can be a sign of “maturity”).
FLASHING SUPERLUMINAL COMPONENTS IN THE JET OF
THE RADIO GALAXY 3C120
J.L. GÓMEZ, A.P. MARSCHER, A. ALBERDI, S.G.
JORSTAD AND C. GARCÍA-MIRÓ
2000, SCIENCE, 289, 2317 96 María Rosa Zapatero Osorio Centro de Astrobiología (CSIC-INTA, Madrid)
What was the problem you had Observations were made in the Galaxy. Several groups of theoretical to face? red-visible and near infrared scientists are trying to model and Are there isolated bodies with masses wavelengths, where it is expected that understand the formation smaller than 13 times that of Jupiter, these very low-mass bodies emit most mechanisms that lead to “isolated in other words, planets that do not of their energy by gravitational planets”. Deeper and more recent orbit any other star? If they exist, contraction. This survey resulted in explorations carried out in the what is the ratio of these with respect the discovery of a relatively high Orionis cluster indicate that bodies to other more massive bodies? How number of “isolated” planetary mass with masses about 3 times that of did they form so that they are now candidate members of the cluster, Jupiter exist, likely to be bodies with “isolated”? What are their physical with masses in the range 5 to 15 the smallest mass directly properties? times that of Jupiter. In addition, the “photographed” outside the Solar first spectra of three of these objects System. What was the solution to this were presented, confirming their cold problem and the contribution atmosphere. Which are the main problems this paper made to the area of in this area of Astrophysics and expertise in which it is framed? Since the paper was published, have what are the expected discoveries We explored in depth a very young there been significant advances in the coming years? region of the sky, virtually a birthplace in this specific area? The formation mechanisms of of stars and brown dwarfs, well- Yes, later other research teams have isolated planets are not known known by our team: the Orionis found bodies with similar masses in with certainty, although there are star cluster, with an age of only 3 other young regions of the sky, which several different theoretical works million years (more than 1,000 times show that the formation of these very that try to explain their existence in younger than the Solar System). low-mass objects is common in our young regions of star formation none 97 Astronomy made in Spain
How did it influence your professional career? Have you continued in that line of work? Has it opened new perspectives or later did you dedicate yourself to other topics? Yes, I have continued in this line of work.
Do you have any anecdote related to this paper’s gestation and publication that you think is worth telling? There are no anecdotes, except for the great observational effort (the need of nights with good seeing and transparency, data should be very deep), and the satisfaction of the whole team when discovering one Figure 1. Orion constellation (background image) of which are confirmed at this time. candidate and then another, then over which the position of the young star cluster A very important piece of another and one more candidate after around the Û Orionis star is highlighted (image on information in Astrophysics is the the data reduction. the left). Three isolated planets with masses ranging population census of all the bodies from 5 to 15 times that of Jupiter, which probably belong to the Û Orionis cluster, are marked with (stars, brown dwarfs and planets) arrows. Courtesy of Gabriel Pérez (IAC). that are formed from a molecular DISCOVERY OF YOUNG, ISOLATED PLANETARY MASS cloud. Any model should reproduce OBJECTS IN THE Û ORIONIS STAR CLUSTER the observed relative number M.R. ZAPATERO-OSORIO, V.J.S. BÉJAR, E.L. MARTÍN, of these three types of bodies. Is there R. REBOLO, D. BARRADO AND NAVASCUÉS, C.A. a mass limit for the formation of BAILER-JONES AND R. MUNDT “isolated planets”? If so, what is the 2000, SCIENCE, 290, 103 limit? 98 Garik Israelian Instituto de Astrofísica de Canarias (Tenerife)
What was the problem you had isotope fingerprints in the spectrum Since the paper was published, have to face? of HD 82943 was a surprise. We there been significant advances When examining the VLT (ESO, calculated that in order to leave such in this specific area? Chile) spectra of the star HD 82943 a mark on the spectrum of the star, We have confirmed the presence (with a planetary system), we found some 3.2 1044 atoms of 6Li would of 6Li in this star with even better that they showed the unmistakable be necessary, an incredible amount. quality spectra. Other groups tried fingerprint of lithium-6 (6Li), an And this was crying out for an to detect 6Li in other planetary isotope of this element which should explanation. systems. In some cases there are not appear in a “mature” star like HD “signs” but there is not a clear 82943, because lithium-6 is extremely What was the solution to this detection. “fragile” and, although it can be a part problem and the contribution It is a very complicated project of the primordial material that forms this paper made to the area of and requires a lot of work with very a star, it cannot live for long. expertise in which it is framed? high-quality spectra and very well In stars similar to the Sun, any As planets are very far from reaching modelled synthetic spectra. atom of 6Li would disappear during the temperatures of the stars, they the first million years of the stars can easily preserve the initial amount Which are the main problems in this lifetime: Strong gas currents would of this isotope. area of Astrophysics and what are the carry 6Li to the inner layers of the Therefore, things would start to expected discoveries in the coming star where the temperatures are 5, 10 make sense and the hypothesis of years? or 15 million degrees. 6Li can not engulfed planets arises in a natural The two fundamental problems in this resist temperatures above 1.5 million way: The simplest way to explain the field are the identification of weak lines degrees; beyond this temperature it is observations is that one or more and possible blends with the lithium destroyed. Therefore, finding this planets have fallen into the star. lines. The convection processes can 99 Astronomy made in Spain
Figure 1. Artist’s impression of a planet falling into its star, as seen from a third planet. Courtesy: Lynette Cook.
cause asymmetries in the spectral lines the theoretical lists of spectral lines and that can therefore affect the and also studied the asymmetries of EVIDENCE FOR PLANET ENGULFMENT 6 detection of the Li isotope. iron lines. We will obtain the first BY THE STAR HD 82943 results in a couple of years or so. G. ISRAELIAN, N.C. SANTOS, M. MAYOR How did it influence your AND R. REBOLO professional career? Have you Do you have any anecdote related 2001, NATURE, 411, 163 continued in that line of work? Has to this paper’s gestation and it opened new perspectives or later publication that you think is worth did you dedicate yourself to other telling? topics? The news about our discovery had Yes, I have continued to work on this a great impact and was featured in topic. We are still analysing the 6Li in newspapers, on television, radio the stars with planets. We improved and the internet. 100 José María Torrelles Arnedo Institut de Ciències de l’Espai (CSIC-IEEC, Barcelona)
What was the problem you had observed a massive protostar discover a water-vapour spherical to face? candidate (15 times the mass of the bubble expelled by another stellar Stars similar to the Sun are formed Sun) in the Cepheus region, which embryo in the vicinity of HW2. This by an accretion process, whose first was thought to be surrounded by an bubble, ejected 33 years ago, has stage is the collapse and accretion disk. We decided to observe been expanding through the fragmentation of interstellar clouds this region through the emission interstellar medium at a speed of gas and dust. The material of water vapour molecules with the of 32,000 km/h, reaching a size of accumulates in the centre, forming radio telescope system VLBA (Very 18,000 million kilometres, a “protostar” or stellar embryo. One Long Baseline Array) with the aim comparable to the size of our Solar part of the unused material is ejected of studying the structure and System, but preserving a perfect at high speeds in the form of jets, kinematics of the gas in the disk. The spherical form. Up to now it was while the rest is accumulated around VLBA has the capacity to resolve known that when most stars are born the protostar, forming a rotating very small details, 200 times better its main feature is that they eject disk. Later, the matter from this disk than the Hubble Space Telescope. large amounts of matter into the falls into the protostar and this interstellar medium in the form of evolves into a star surrounded by a What was the solution to this jets, highly collimated and moving at planetary system. However, the birth problem and the contribution supersonic speeds, in agreement with of stars much more massive than the this paper made to the area theoretical predictions. Sun was, and still is, a mystery in of expertise in which it is framed? That is why we were very surprised many aspects. Our research group Although the data we obtained were to find such a perfect expanding thinks that those stars can be formed consistent with the presence of a disk spherical bubble, something very by accretion, in a similar way to the around a massive protostar called difficult to explain from a theoretical less massive stars. In 1997, we HW2, our big surprise was to perspective. Our contribution was to 101 Astronomy made in Spain
find, by chance, a new phenomenon that may have to do with an unknown physical process that causes the ejection of matter in a very early stage of the stellar embryo evolution, long before the influence of the protoplanetary disks is evident.
Since the paper was published, have there been significant advances in this specific area? Our observations and results motivated other research groups to make similar observations of the water-vapour emission in other star forming regions using the VLBA. This instrument, which belongs to the National Radio Astronomy Figure 1. Image of the infrared emission of the gas and dust cloud in the Cepheus constellation, located some Observatory (USA), is composed of 2,000 light years from Earth, where many stars are being born. The first zoom-in of the image shows the detail ten radio telescopes (each with a dish of one of the stellar embryos (the bright and elongated structure that can be appreciated in the centre), surrounded 25 meters in diameter): One located by strong water vapour emission (indicated with crosses). The second zoom-in of the image (on the right top in Hawaii, another in St. Croix (U.S. corner) recreates the location of the enigmatic stellar embryo that has produced a spherical bubble of water vapour around it, which continues expanding after reaching a size similar to our Solar System. The discovery of this Virgin Islands) and the other eight in bubble has been made using the VLBA radio telescope system at the National Radio Astronomy Observatory the North American continent. The (NRAO), observatory that depends on NSF (USA). (Infrared image credit: Klaus-Werner Hodapp). ten radio telescopes are remotely controlled. As a result of those new observations, two additional protostars has been found that eject gas in multiple directions into the interstellar medium, almost isotropically (although the sphere 102 Spanish Astronomical Society
is not as perfect as in the case of the results indicate that the bubble, Universitat de Barcelona, and Institut Cepheus region). So far, we know although it still preserves some de Ciències de l’Espai (CSIC). that the water-vapour emission is the features that we presented in our product of very violent collisions in Nature paper, is being dissipating Do you have any anecdote related to the interstellar medium gas. into the interstellar medium. this paper’s gestation and publication that you think is worth telling? Which are the main problems in this How did it influence your Perhaps it is not an anecdote, but area of Astrophysics and what are professional career? Have you I do remember the first big surprise the expected discoveries continued in that line of work? Has when coming across this discovery, in the coming years? it opened new perspectives or later which we were not looking for, and The main problem of this new did you dedicate yourself to other the subsequent joy shared by all the phenomenon is to explain, from a topics? members of the team. Undoubtedly, theoretical point of view, the physical We exploited the potential of the so far this has been the most complex origin of isotropic ejections during VLBA and its associated reduction research project I have had the good the first stages of stellar evolution. So software to carry out the observations fortune to be part of with our whole far, we do not have a conclusive of the Cepheus region. As a result, team. answer. In the next few months we all the members of the group that are expecting to explain the evolution participated in this experiment have of the spherical bubble found in the the motivation to continue in this SPHERICAL EPISODIC EJECTION OF MATERIAL FROM A Cepheus region, from its discovery to line of research, and at present it is YOUNG STAR the present day. In order to do that, one of the priorities of our Spanish J.M. TORRELLES, N.A. PATEL, J.F. GÓMEZ, P. T. P. H O, we are in the process of analysing research group composed by L.F. RODRÍGUEZ, G. ANGLADA, G. GARAY, L. new observations made in the region researches from the Instituto de GREENHILL, S. CURIEL AND J. CANTÓ with the VLBA. Very preliminary Astrofísica de Andalucía (CSIC), 2001, NATURE, 411, 277
103
Luis Felipe Miranda Palacios Instituto de Astrofísica de Andalucía (CSIC, Granada)
What was the problem you had What was the solution to this distances, so we proposed that the to face? problem and the contribution jets were involved in the excitation. Planetary Nebulae (PNe) are formed this paper made to the area of We also observed OH masers in when the envelope ejected during the expertise in which it is framed? K3-35. The OH emission at 1,665 earlier red giant phase is ionized by In 1999 we used the Very Large MHz was circularly polarized, the radiation from the remnant central Array (VLA) to obtain simultaneous implying that we had detected a star. In 1997 we obtained images and data of the water masers and of the magnetic field in a PN for the first analysed spectra of K3-35, an object radio continuum (which traces time. whose nature was controversial: PN or the ionized region) in K3-35. This forming star? Our analysis, published technique allows us a very precise Since the paper was published, have in 1998, conclusively proved that K3- measurement of the relative positions there been significant advances 35 is a planetary nebula. This result of both emissions. Water masers were in this specific area? was not consistent with the existence of indeed associated with K3-35, which The existence of PNe with water water maser emission towards K3-35, became the first PN discovered with masers is a fact today. As well as as detected by other researchers. Water water masers. The masers were K3-35, our group has detected two masers are abundant in red giants but located in a disk with a radius of 85 other PNe and several PN candidates were inconceivable in PNe where AU (1 astronomical unit is equivalent with water masers. We know that the physical conditions for such an to 150 million kilometres) and, ejections of matter with non emission do not exist. However, the surprisingly, also at a distance of spherical geometry, probably in the existing observations did not have 5,000 AU from the centre, at the tips form of collimated jets, represent a enough spatial resolution to precisely of two collimated jets. The physical crucial role in the formation of water locate the masers with respect conditions to excite the water maser masers in these objects. We have to K3-35. do not exist at such enormous a basic understanding of how water 105 Astronomy made in Spain
masers evolve in these phases of We think that, in the formation stellar evolution, and there is of PNe, multiple physical factors are evidence that these masers are involved: Interaction between the associated with relatively massive winds of the central star, magnetic stars (about 4-5 solar masses). fields, binary nature of the central Magnetic fields have been detected star and collimated jets. In the next and measured in several PNe, few years we expect significant including a very detailed study of advances in our knowledge of the K3-35 carried out by our group, and origin of collimated jets, mainly in their central stars. The existence through the study of water masers, in and magnitude of magnetic fields the detection of binary central stars give observational support to and in the influence of magnetic theoretical models for the formation fields in the formation and evolution of PNe that incorporate magnetic of PNe. fields. How did it influence your Figure 1. Water-maser emission and OH maser emission in the planetary nebula K3-35. The colour Which are the main problems professional career? Have you images represent the radio continuum emission in this area of Astrophysics continued in that line of work? Has at 3.6 cm (large image) and at 1.3 cm (small image), and what are the expected it opened new perspectives or later that trace the ionized region of the object. The reddish discoveries in the coming years? did you dedicate yourself to other region in the image at 3.6 cm represents the collimated Nowadays we know that PNe present topics? bipolar jet of K3-35. The red dots indicate the water very complex structures: Non- Water-maser detection in K3-35 led maser positions (regions N, C, S1 and S2). The blue crosses indicate the OH maser emission at 1,665 MHz, spherical, multipolar or highly us (an increasingly large group of and the blue triangles indicate the OH maser positions collimated, envelopes and high researchers) to search for this at 1,667 MHz. In the 3.6 cm image, the distance velocity bipolar jets, in many cases emission in other PNe. We already between the N region and the centre of the object is with direction changes and/or several know three PNe and have several about 5,000 AU. In the 1.3 cm image, the distance orientations within the same PN. other PN candidates with water between the masers and the centre is about 85 AU. These components cannot be maser emission. We are also searching explained with the classical concepts for and detecting water masers in of late stellar evolution and represent objects in an evolutionary phase a challenge for theoretical models. immediately prior to the PN stage. 106 Spanish Astronomical Society
The relevance of all these objects has led us to observe them in other wavelengths (infrared, optical, X-rays) and with several observational techniques (images, spectra) to obtain more information about their characteristics and properties. K3-35 itself has been the target of many observations, by our group and other groups. We can say Figure 2. OH maser emission spectra at 1,665 MHz. that water detection in K3-35 has The blue spectrum shows the left circular polarized opened a new research line whose emission (LCP) and the red spectrum shows the right circular polarized emission (RCP). The difference results are building the base of new between the two spectra indicates the presence of future projects. a magnetic field.
WATER-MASER EMISSION FROM A PLANETARY NEBULA
WITH A MAGNETIZED TORUS
L.F. MIRANDA, Y. GÓMEZ, G. ANGLADA,
AND J.M. TORRELLES
2001, NATURE, 414, 284
107
Javier Trujillo Bueno Instituto de Astrofísica de Canarias (Tenerife)
What was the problem you had detection of polarization due to the absence of magnetic fields in the to face? Zeeman effect implies the presence observed plasma. The problem was the determination of a magnetic field. The bad news is of the magnetic field in the solar the following: On the one hand, What was the solution to this atmospheric plasma, both in plasma diagnostic techniques based problem and the contribution that structures embedded in the in the polarization of the Zeeman your two Nature papers made to chromosphere and the corona, and in effect are not very practical for the the area of expertise in which they the apparently non-magnetic regions determination of the magnetic field are framed? of the underlying photosphere. For in hot plasmas (like the ones in the The solution to the problem of the this, it is necessary to measure and Sun’s chromosphere and corona) magnetic field determination in those interpret the polarization of the because the larger the thermal plasma regions of the solar sunlight in spectral lines originating broadening of the spectral lines atmosphere involved the in its atmosphere. the lower the amplitude of the development and application to The physical mechanism that polarization signal; on the other spectropolarimetric observations produces polarization in a spectral hand, the Zeeman effect as a plasma of new diagnostic techniques based line is the Zeeman effect; this effect diagnostic technique tends to be on the Hanle effect (Figure 1). had been used to carry out most “blind” to the presence of highly The investigation we carried out of the research until then. The tangled magnetic fields below the on the magnetism of the apparently polarization produced by the Zeeman resolution element of current non-magnetic regions of the solar effect is due to the energy splitting telescopes. photosphere (Trujillo Bueno, of the upper and/or lower magnetic In short, the lack of detection of Shchukina and Asensio Ramos 2004) levels of the spectral line considered. polarization induced by the Zeeman consisted in measuring the linear The good news is that the simple effect does not necessarily imply the polarization amplitudes produced by 109 Astronomy made in Spain
scatterig processes in carefully produced in the external regions selected atomic and molecular of the solar atmosphere (the spectral lines and comparing them chromosphere and the corona). with the ones that the Sun would In our second publication (Trujillo produce if it were not magnetized. Bueno et al. 2002) we managed to The difference between the observed predict (with calculations based on polarization and the polarization the quantum theory of polarization) corresponding to the non-magnetized and discover (with observations case is due to the presence of carried out with the Tenerife Infrared a “hidden”, spatially unresolved Polarimeter developed by the IAC) magnetic field. We managed to the existence of peculiar polarization Figure 1. The upper panel shows that light determine its intensity thanks to our signals in the spectral lines of the scattering processes by atoms in a stellar numerical simulation of the neutral helium triplet at 10830 atmosphere produce linear polarization in spectral polarization induced by scattering Angstroms, when observing huge lines. The lower panels indicate that this processes, and its modification by the plasma structures of the solar corona polarization is modified by the presence of a magnetic field (Hanle effect). For the situations Hanle effect, in three-dimensional (prominences) where it was believed represented in both lower panels, the modification hydrodynamical models of the solar that such a polarization should be with respect to the non-magnetized case of the photosphere. The mean magnetic insignificant. In particular, we proved upper panel is a decrease in the polarization field intensity we derived is very that the Hanle effect can be used as a amplitude and a rotation of the polarization significant (about 100 gauss), and it magnetic field diagnostic technique direction. Note that, even for the case where both magnetic polarities of the lower panels are mixed is much more intense in the for the whole solar disk and not only together below the observational resolution limit, intergranular regions than in the in 90º scattering geometry, as was we still have a measurable effect as the granular regions of the solar previously thought. We also polarization amplitude of the observed light photosphere. The intensity and discovered a new physical mechanism continues to be lower than that corresponding to ubiquity of this unresolved magnetic that generates polarization in spectral the non-magnetized case of the upper panel. field implies that the apparently quiet lines (the selective absorption of regions of the solar atmosphere polarization states). This is very contain an enormous amount of difficult to study in terrestrial magnetic energy, so large that only a laboratories, as it requires the small fraction would be sufficient to observation of the light that is balance the radiative energy losses partially absorbed by a very-low 110 Spanish Astronomical Society
density and large dimension plasma (Figure 2). Besides, for this to be produced, the atoms in the plasma under study must be excited by anisotropic radiation pumping, something that happens naturally in the external regions of the stellar atmospheres. The importance of this discovery lies in the fact that it enables a reliable study of magnetic fields in the solar chromosphere and corona, as well as in other Figure 2. Illustration of the polarization of the emergent spectral line radiation resulting from 90º and forward astrophysical systems such as that of scattering processes, when these scattering processes take place in an optically thin plasma permeated by a horizontal supernova atmospheres. For example, magnetic field. The left panel refers to a spectral line whose upper level has an angular momentum J(up)=1 and its recent applications of our diagnostic lower lever J(low)=0, while the right panel corresponds to a line with J(up)=0 and J(low)=1. In each case, the anisotropic illumination of the atoms produces the atomic polarization shown (see the differences among the technique are making it possible to populations of the three magnetic sublevels in each atomic level with J=1). Therefore, in the left panel the linear study the strength and geometry of polarization observed is due to selective emission of polarization states, while in the right panel the only mechanism in the magnetic field that confines the action is selective absorption of polarization states. For this reason, in the right panel, an observer placed at the position plasma of the enormous solar (1) sees that light scattered at 90º by an optically thin plasma is not polarized while, at position (2), he/she sees linearly prominences; these prominences polarized light perpendicular to the magnetic field. usually cause impressive coronal mass ejections that sometimes affect the near-Earth environment.
Since the publication of these two papers, have there been significant advances in this specific area? Yes, in the first place, today many scientists who work on solar and stellar physics are applying our plasma diagnostic techniques to 111 Astronomy made in Spain
deduce the magnetic field from the signals with a spatial resolution of main problem is that there are very observations of the polarization 100 km over the solar atmosphere few scientists working in this caused by the joint action of the and with a temporal resolution of the fascinating research field, which Hanle and Zeeman effects, and this order of seconds. Fortunately, several requires the careful combination of is producing an important advance in European countries are working atomic physics, numerical simulation our empirical knowledge of the together on the design of what could and spectropolarimetric observations magnetic fields that confine the be the European Solar Telescope with sophisticated instruments. plasma of the chromospheric and (EST), although, provided the coronal structures. In addition, some funding for its construction on one How did it influence your space agencies, as the Japanese, are of the observatories in the Canary professional career? Have you planning a new solar space telescope; Islands is obtained, it would not be continued in that line of work? Has one of the two possible options operational before 10 years from it opened new perspectives or later includes sophisticated instruments to now. Another good piece of news is did you dedicate yourself to other observe the polarization signals in that, as I mentioned before, the topics? spectral lines that we have Japanese space agency is very I think it had a significant influence, investigated in our research. Such interested in equipping its next solar although I do not believe that a good spectropolarimetric observations telescope with new instruments paper published in Nature or Science would give rise to an unprecedented designed to measure the polarization is better than a good paper published development in solar and stellar signals resulting from the joint action in other journals like The physics. of the Hanle and Zeeman effects in Astrophysical Journal o Astronomy several spectral lines. In fact, a few and Astrophysics. Papers published in Which are the main problems months ago, in an important meeting Nature and Science are like luxury in this area of Astrophysics and in Tokyo, scientists from all over the press releases but not everything a what are the expected discoveries world have discussed in depth the scientist achieves is suitable to be in the coming years? two ongoing proposals for such a published in those interdisciplinary Regarding telescopes, the main space telescope known as SOLAR-C. journals. It is good to publish in problem lies in that we do not have From the theoretical point of view, them from time to time, provided any large-aperture solar telescope on including the numerical simulation that they are good papers, also Earth (for example, with a 4 meter of the processes of the generation and interesting for scientists who work in diameter), which is essential for transfer of polarized radiation in other disciplines, but the aim should detecting many of those polarization magnetized plasmas, perhaps the always be to contribute to the 112 Spanish Astronomical Society
development of science and publish the scientific results clearly and SELECTIVE ABSORPTION PROCESSES AS THE ORIGIN OF rigorously in the optimum journal PUZZLING SPECTRAL LINE POLARIZATION FROM THE SUN for each particular research work. J. TRUJILLO BUENO, E. LANDI DEGL'INNOCENTI, Regarding the second question, we M. COLLADOS, L. MERENDA AND R. MANSO SAINZ. continue working with great interest 2002, NATURE, 415, 403 in this line of research but we are trying to facilitate the application of A SUBSTANTIAL AMOUNT OF HIDDEN MAGNETIC ENERGY these developments achieved in solar IN THE QUIET SUN and stellar physics to other fields of J. TRUJILLO BUENO, N. SHCHUKINA Astrophysics. AND A. ASENSIO RAMOS
2004, NATURE, 430, 326
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Margarita Hernanz Carbó Institut de Ciències de l’Espai (CSIC-IEEC, Barcelona)
What was the problem you had transfer is relatively unknown and it Oph, which had exploded in 1998, to face? is only observable in X-rays. This is with the XMM-Newton satellite Although at first sight all the stars why we decided to observe the X-ray produced surprising results, as we did in the sky appear to be unchanging emission, with the aid of satellites, of not detect the hot atmosphere of the and with a constant brightness, often some novae after they have exploded. white dwarf but a different kind of there are stellar explosions that X-ray emission, characteristic of the extremely increase the luminosity What was the solution to this violent fall of matter onto the surface of some objects. Nova explosions are problem and the contribution of a white dwarf with an intense an example. They are produced when this paper made to the area of magnetic field. Therefore, we a white dwarf star accretes hydrogen- expertise in which it is framed? deduced that the transfer of matter rich matter from a close companion X-rays are the only way to study the had been re-established as early star. The progressive accumulation phases after the nova explosion; once as 2.7 years after the explosion. of mass on the surface of the white the envelope has been ejected, the dwarf ends up provoking the hydrogen nuclear burning continues Since the paper was published, have uncontrolled nuclear burning of quiescently on the surface of the there been significant advances hydrogen, with the resulting ejection white dwarf; this keeps the in this specific area? of the envelope of the star at atmosphere very hot and it emits Since the year 2002, there have been velocities of several hundreds or X-rays. The European Space Agency’s important advances in the field thousands of km/s, accompanied by XMM-Newton (X-ray Multimirror of X-ray observations, since both a large increase in luminosity. The Mission) satellite offers a unique XMM-Newton and Chandra turn-off of nuclear burning that opportunity to study this emission satellites have provided new excellent causes the nova to fade and return thanks to its large collecting area. quality data. High-resolution spectra to its original state of quiescent mass Our observations of the nova V2487 have been obtained, enabling the 115 Astronomy made in Spain
transfer from the imaging era to the should be overcome in the near spectroscopy era in the X-rays, as future. Both the constant happened decades ago with optical improvement of computer power and astronomy. Knowing the amount of the development of new numerical energy per unit time emitted at each techniques will make it possible to frequency or wavelength, through the tackle the explosion phenomenon study of emission/absorption lines, in three dimensions, with reasonable Figure 1. Artist’s concept of a white dwarf capturing allows us to study the underlying calculation times. Regarding X-ray matter from its companion. The result of this physical phenomena. In the case of observations, the level of detail that accumulation of matter is a nuclear explosion known as nova. novae, we have an increasing amount is being achieved with X-ray of information regarding the very hot spectrometers on board XMM- atmosphere of the white dwarf and Newton and Chandra is a challenge the surrounding material, both the for theoretical interpretation, and material that is ejected during more complete X-ray emission the explosion and the material that models are necessary, including very falls onto the white dwarf again, hot white dwarf atmosphere models transferred from its companion. and mass accretion models in the presence of intense magnetic fields. Which are the main problems in this area of Astrophysics and what are How did it influence your the expected discoveries in the professional career? Have you coming years? continued in that line of work? Has In the field of stellar explosions, it opened new perspectives or later several fundamental problems remain did you dedicate yourself to other to be solved. On the one hand, topics? theoretical models of the explosion In my professional career I have itself still include some continued working in research topics simplifications, such as the along the path opened by the paper assumption of spherical symmetry I published in Science in 2002. It is and therefore the resulting one- known that, in science, a single dimensional calculation, which object does not define a 116 Spanish Astronomical Society
phenomenon, therefore more cases than usual, because the authors were should be found to be able to two women. Although this is establish the general or exceptional something that should not be nature of the event. The X-ray surprising, it was much highlighted observatory XMM-Newton has in the media, with sentences like allowed us to apply the same study “two women astronomers discover…” of the fading and subsequent The female authorship seemed to be recovery of novae to other objects. So more important than the content of far, we have not found any object of the paper. Besides, it stressed the fact the same type as V2487 Oph, but we that the authors were my thesis have indications that they must exist student —Glòria Sala— and me Figure 2. Image of the Nova Oph 1998 obtained since we have detected similar —her thesis director— something in X-rays with the instrument EPIC on board the objects. In addition, we want to take that it is actually quite usual in our XMM-Newton observatory. advantage of future space research field. In brief, there were instruments both in the X- and several interviews about work and gamma-ray ranges. In fact, we have family “conciliation”, etc., that become involved in their design probably would not have been made to ensure that it will be possible to if the authors were not women; this achieve the best quality science. shows that we have not yet reached equality. Do you have any anecdote related to this paper’s gestation and publication that you think is worth A CLASSICAL NOVA, V2487 OPH 1998, SEEN telling? IN X-RAYS BEFORE AND AFTER ITS EXPLOSION The publication of this paper had M. HERNANZ AND G. SALA quite an impact in the media, bigger 2002, SCIENCE, 298, 393
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Jordi Miralda Escudé Institució Catalana de Recerca i Estudis Avançats (ICREA) Institut d’Estudis Espacials de Catalunya (IEEC, Barcelona)
What was the problem you increase in the accuracy of the observing the background radiation, had to face? measurement of the opacity of the we can see the fraction of that I had to write a paper summarizing Universe since the moment the first radiation that has been absorbed the advance in our scientific knowledge stars were formed. We can measure on its way towards the Earth, as the about the first stars and galaxies formed the opacity of the Universe towards the radiation passed through the in the Universe, and the way they furthest radiation that we can reionization epoch and was scattered influenced the intergalactic medium. observe, that is called the “cosmic by the ionized matter. This gives background radiation” and it has the Universe a certain opacity. What was the solution to this been filling all the space since the Big The first measurements suggested problem and the contribution Bang. Background radiation started an opacity of 15%. This seemed to this paper made to the area of to propagate through space freely indicate that the first stars had been expertise in which it is framed? when the Universe was 400,000 years formed very early compared with The contribution was to make a old; at that moment the temperature theoretical predictions of the review of the work done until that had dropped enough for atoms to structure formation in the Universe, moment by many scientists and the start forming for the first time. although the measurement error was things we had learnt from different Before that time, the Universe was very high. Subsequent higher observations. opaque, since ionized matter (with precision measurements have atomic nuclei and free electrons) is indicated that the opacity is about Since the paper was published, much more opaque than atomic 8%, a value more in agreement with have there been significant advances gases. However, when the first stars the expectations. in this specific area? and galaxies were formed, matter Yes, there have been quite a few. One became ionized again; this is the of the most important ones was the so-called reionization epoch. When 119 Astronomy made in Spain
Which are the main problems in this area of Astrophysics and what are the expected discoveries in the coming years? The problems are to find out what type of stars and galaxies first formed, the age of the Universe when that happened and the type of radiation they emitted that ionized the Universe. We hope several new discoveries in this field will advance our knowledge during the next decade. Infrared telescopes will allow us to discover increasingly distant galaxies, observed when the age of the Universe was less than 1 billion years and the first galaxies were forming. We also expect to be able to observe the largest stellar explosions, called gamma-ray bursts, which can Figure 1. Sketch of the evolution of the Universe. Courtesy of the WMAP consortium. also be observed at the largest possible distances due to their incredible luminosity; the detection of these bursts shows the presence of massive stars and allows us to examine the state of the surrounding medium. Another important advance is going to be the probable detection of hydrogen in the 21-cm line from intergalactic atomic matter in the 120 Spanish Astronomical Society
early Universe, at the epoch when the Do you have any anecdote related From there, I was able to write first stars were forming, using radio to this paper’s gestation and the ideas I had in mind very quickly. telescopes observing at very low publication that you think is worth At the end of the paper I mentioned frequencies. This would represent telling? her name in the acknowledgments. a great milestone for observational When I was writing the paper, I was After its publication, I gave her cosmology. living in the US state of Ohio and a copy but I think she never realized I had a Swiss girlfriend who was her name appeared in the How did it influence your a professor at the Chinese Literature acknowledgements of a paper professional career? Have you Department at the University. The in Science. continued in that line of work? Has subject of my paper was obviously very it opened new perspectives or later far from her specialization. However, did you dedicate yourself to other when the deadline for submitting the THE DARK AGE OF THE UNIVERSE topics? paper was only ten days away and I J. MIRALDA-ESCUDÉ I am still thinking and investigating was getting nervous because I had not 2003, SCIENCE, 300, 1904 on this topic but I also work written anything yet, she gave me an on other issues. idea on how to start it.
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Josep Miquel Girart Medina Institut de Ciències de l’Espai (CSIC-IEEC, Barcelona)
What was the problem you had What was the solution to this Array, in Mauna Kea, Hawaii), the first to face? problem and the contribution set of antennas that reaches wavelengths Stars are formed by the collapse (by this paper made to the area of below the millimetre range. Taking their own gravity) of giant interstellar expertise in which it is framed? advantage of the sensitivity of this radio clouds of molecular gas and dust The interstellar magnetic field can telescope to the radiation generated by particles. These clouds are opaque to only be studied if it is possible to interstellar dust, we pointed it towards visible radiation because of the detect the polarized radiation. The one of our best candidates: a region presence of dust grains. So, if we want polarized emission is only a small where stars like the Sun are forming, to study the star formation we should fraction of the total radiation that which is at a distance of only 1000 observe star-forming regions in the a telescope receives, which is already light years from the Earth. And we hit infrared or microwave wavelengths. very weak, especially at microwave the bull’s-eye! The images we obtained In the last decades, there have been wavelengths! (This is the reason why clearly showed that the collapse of the important developments in telescopes radio telescopes are usually very large). cloud drags the magnetic field, making and their instrumentation at these A decade ago, we made one of the it to adopt a shape similar to an wavelengths that have made it possible first advances with the BIMA hourglass, as predicted by the models to achieve great advances in our interferometer (Berkeley Illinois that see the magnetic field as the knowledge of star formation. But Maryland Association, California). “controller” of the collapse. there is still a long way to go, and At these radio telescopes, we installed there are many unanswered questions. a system that detected the polarized Since the paper was published, One of them is: What mechanisms emission of dust grains in molecular have there been significant advances controls the start and subsequent clouds where stars are forming. in this specific area? evolution of the collapse of a gas More recently, a polarimeter was There have been modest advances. cloud: magnetic fields, turbulence…? installed at the SMA (Submillimeter Despite the power of the SMA, the 123 Astronomy made in Spain
number of molecular clouds which are bright enough at submillimeter wavelengths is not very large. So the sample of the study is relatively 34” small. But, little by little, I think that in a few years there will be significant advances.
32” Which are the main problems in this area of Astrophysics and what are the expected discoveries in the coming years? DEC (J2000) Regarding star formation, there are 30” still plenty of controversial or little- known aspects. One is to know if the more massive stars form in the same way as less massive stars, like the 31º13’28” Sun. Another is to know how planets form. The advance in both problems is limited by the enormous difficulty in observing these processes. In this 3h29m10s.8 10s.7 10s.6 10s.5 10s.4 10s.3 10s.2 sense, ALMA (Atacama Large RA (J2000) Millimetre/submillimiter Array), a new interferometer that is being built Figure 1. Image obtained with the SMA at 0.88 mm of the dust emission associated with the region NGC 1333 IRAS 4A, a place where stars like the Sun are forming. The red bars indicate the direction of the magnetic field. in Chile at an altitude of more than 5000 meters above sea level, is going to have a huge impact on the progress of these problems, as well as in many others. There is an important part of the astronomical community that, as we say in 124 Spanish Astronomical Society
Catalan, “espera amb candeletes” (“eagerly awaits”) the commissioning of ALMA.
How did it influence your professional career? Have you continued in that line of work? Has it opened new perspectives or later did you dedicate yourself to other topics? Since we realized the importance of the results, our group has devoted an important part of its research Figure 2. The Submillimeter Array, located atop Mauna Kea in Hawaii, at an altitude of more than 4000 meters. to the study of the magnetic field in molecular clouds, trying to take the most out of the SMA, as well as other instruments which are able living in Hawaii and working we managed to do it and when we to detect the polarized emission for the SMA). For several reasons obtained the first images we of interstellar radiation. we realized that the software immediately realized the importance designed by the SMA for the of the results. Do you have any anecdote related processing of data collapsed with to this paper’s gestation and our data obtained using the publication that you think is worth polarizing system. We did not make MAGNETIC FIELDS IN THE FORMATION OF SUN-LIKE telling? any progress at all in those days, it STARS Our observations were the first was completely frustrating! We had J.M. GIRART, R. RAO AND D.P. MARRONE made with the SMA polarizing to go back to the past, and use older 2006, SCIENCE, 313, 812 system, so we were the guinea pigs. software that worked very well for In Hawaii, I processed the data BIMA, and adopt some routines to obtained from the observations with the specifications of the SMA, the SMA, in collaboration with my without being sure that it would colleague Ramprasad Rao (a Hindu actually work. In the end, 125
Aníbal García Hernández Instituto de Astrofísica de Canarias (Tenerife)
What was the problem you had rubidium-87, 87Rb) in large models of stellar nucleosynthesis, to face? quantities; however, this had never an observational confirmation had We wanted to identify, for the first been observationally confirmed. not been obtained to date. time, the old stars of our Galaxy This work has made it possible to (Asymptotic Giant Branch or AGB What was the solution to this study, for the first time, the late stages stars) with masses between 4 and 8 problem and the contribution of the life of the most massive AGB times that of the Sun, for studying this paper made to the area of stars. Moreover, these stars contribute their chemical composition and the expertise in which it is framed? significantly to enriching the elements produced inside them. This With measurements at radio interstellar medium, therefore it is would allow us to observationally wavelengths and of their infrared crucial to understand what happens prove the theoretical models of the colours we could efficiently isolate inside them and the chemical late stages of the life of stars of this the right stars for the first time. The composition of the material returned type (stellar evolution), as well as the chemical analysis of these stars to the interstellar medium at the end physical mechanisms (stellar allowed us to discover that shortly of their lives in order to understand nucleosynthesis) that convert them before dying they show an the chemical evolution of our Galaxy. into factories of heavy elements, extraordinary amount of rubidium including some very exotic elements (up to 100-1000 times the amount Since the paper was published, like rubidium, zirconium, barium, present in the Sun) on their surface. have there been significant advances strontium, etc. In particular, stellar Although the existence of this type of in this specific area? evolution models predicted more massive and evolved stars, very The results presented in this paper were than 40 years ago that this type of enriched in rubidium, had been not completely explained by stars should produce rubidium predicted, as I mentioned above, the theoretical models available at the (particularly the isotope more than 40 years ago by theoretical time and therefore, this research has 127 Astronomy made in Spain
made it possible for the models to be improved so that they can reproduce the observations. These days, the models have been refined and are able to reproduce the observations of rubidium stars. Also, this type of stars could explain the chemical anomalies that are found in the oldest meteorites in the Figure 2. Sketch of the stellar structure of low and Solar System and, they are starting to be intermediate-mass stars (less than 8 times the mass of the Sun) at the end of the AGB phase. Basically, AGB stars identified in nearby galaxies. are composed of an inert C-O core surrounded by two thin shells rich in helium and hydrogen. On top of this Which are the main problems double shell configuration sits a large hydrogen convective in this area of Astrophysics envelope. Note that the figure is not to scale and, in and what are the expected Figure 1. Rubidium is detected as a very intense particular, the envelope is much larger than the C-O absorption line at a wavelength of 780 nanometres. This core. discoveries in the coming years? is a spectrum of one of the discovered rubidium-rich The fundamental problems are related stars, superimposed on an artist’s impression of an AGB to the faintness of these stars in the star. Image courtesy of the European Space Agency. visible wavelength range and the improvement of the theoretical models. Although this type of stars are present in almost every galaxy, the large distances to other galaxies make
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Planetary Nebula B A F G K M them very difficult to detect, even these stars can be studied in other 6 Phase Transition Time 10 using 8-10 meter diameter telescopes. wavelength ranges such as the 104 AGB Stars Now that we are able to efficiently near-infrared, where we can obtain Horizontal Branch 102 Red Giant isolate the right stars for the first time, information on other chemical Branch 1 it will be possible to detect and study elements. In addition, the L(L.)
-2 Main them in the closest galaxies (the identification of these stars in our 10 White Sequence -4 Dwarfs so-called galaxies of the Local Group). Galaxy as well as the study of their 10 In addition, we will also obtain very chemical composition have opened 5.5 5.0 4.5 4.0 3.5 Log T (K) important information at other new research fields like for example, wavelengths that will allow us to fine- their role in the chemical evolution Figure 3. H-R (Hertzsprung-Russell) diagram that tune the current theoretical models, of other galaxies and the knowledge shows the stellar luminosity (in solar luminosities) versus something that will help to better of the environment where our Solar temperature (in Kelvin). The main evolutionary phases in the life of a star of low and intermediate-mass (less understand the late stages of life of these System formed. that 8 times the mass of the Sun) are shown. After the stars depletion of hydrogen (main sequence) and helium (Red
Giant Branch) in their cores, these stars evolve towards How did it influence your RUBIDIUM-RICH ASYMPTOTIC GIANT BRANCH STARS the AGB. Finally, they form planetary nebulae and end professional career? Have you D. A. GARCÍA HERNÁNDEZ, P. GARCÍA LARIO, B. PLEZ, their lives as white dwarfs. continued in that line of work? Has it F. D’ A NTONA, A. MANCHADO AND J.M. TRIGO opened new perspectives or later did RODRÍGUEZ you dedicate yourself to other topics? 2006, SCIENCE, 314, 1751 This work has allowed me to continue in this line of research since
129
María Teresa Beltrán Sorolla INAF-Osservatorio Astrofisico di Arcetri (Florencia, Italia)
What was the problem you had What was the solution to this rotation, infall and outflow. We, to face? problem and the contribution therefore, confirmed the prediction The problem was to understand how this paper made to the area of of the theory that proposes that massive stars form; these are stars with expertise in which it is framed? massive stars would form in a similar masses 8 times larger than the mass In the low-mass star formation way to the Sun. of the Sun. High-mass stars are key process, infall, outflow and rotation ingredients of galaxies, since they play very important roles. Despite Since the paper was published, control their appearance and evolution, the fact that rotation, outflow and, have there been significant advances inject energy into the interstellar to a lesser extent, infall, had already in this specific area? medium and regulate the star been detected in massive star forming In the last years, evidence of infall formation rate. Furthermore, they are regions, they had never been had been found in a very limited responsible for the production of heavy observed simultaneously in the same number of massive stars, but still it is elements necessary for life, like oxygen, stellar object before. possible to count on the fingers of carbon, calcium or iron. Despite the In our study we looked for one hand the massive stars where importance of these stars, very little observational evidence of these these three basic elements of star is known about their formation movements around a very young formation have been clearly detected. mechanisms. One of the theories stellar object in the process of As statistics are so poor, it is proposes that massive stars form as formation called G24.78+0.08 A1, difficult to derive important a result of gravitational collapse, in a which has a mass of about 20 solar parameters in the star formation similar way to the formation of our masses. These observations revealed, process, like for example, the Sun; others, however, propose that for the first time, the simultaneous accretion rate at which the material massive stars form by coalescence presence of these three basic is incorporated into the forming star. of many lower mass stars. ingredients in star formation: The fact that there are so few 131 Astronomy made in Spain
examples is mainly due to the facilities already working, like the difficulty to study massive star infrared observatory Herschel forming regions, owing to their small and the Gran Telescopio Canarias number when compared to the (GTC), or those that are currently number of known low-mass star being constructed, such as the forming regions, the larger distances antennas of the ALMA to us and the fact that massive star interferometer. They will allow lifetimes are very short. us to observe the area immediately surrounding the star and to check Which are the main problems if disks exist. in this area of Astrophysics Figure 1. Sketch of star formation. The protostellar and what are the expected How did it influence your cloud collapses and the presence of rotation makes a disk discoveries in the coming years? professional career? Have you appear. Part of the cloud material is ejected in two Our study confirmed that stars up continued in that line of work? Has outflows perpendicular to the disk, while the material to 20 solar masses could form by it opened new perspectives or later of the disk is accreted by the star. accretion or infall of material did you dedicate yourself to other through a rotating disk around the topics? star. However, it remains to be I have continued with this research proved if more massive stars also line, extending the search of infalling form in this way. No rotating and material to other massive stars. infalling disks, as those observed in Following the hypothesis that lower mass stars, have yet been massive stars form like low-mass stars, detected towards the most massive we have started to carry out studies stars. For this reason, some theories on the importance of the magnetic propose that the most massive stars field. For low-mass stars we know form by different mechanisms, like that the magnetic field plays a for example merging of low-mass fundamental role in the formation stars. process but its importance has not yet In the next few years there will be been proven in the case of massive advances in this field, with the new stars. 132 Spanish Astronomical Society
Do you have any anecdote related G24.78+0.08 to this paper’s gestation and publication that you think is worth 0.05 1 telling?
0 0 Shift along the plane of toroid (“) The publication of this paper had a great impact worldwide, something -0.05 -1 that seemed impossible taking into 0.05 1 account that it was an Astronomy
(J2000) 0 0 paper. Out of curiosity, I started to α -1 search the internet for papers about -0.05 our discovery and I found some 0.05 1 written in Arab, Chinese, Japanese, 0
Shift along the plane of the toroid (pc) along the plane of toroid Shift 0 Thai, Korean, Finnish, etc., just to -1 cite the most exotic ones. The most -0.05 curious one was a paper in a Nigerian -7º12'12" -7º12'10"18 -7º12'12"h36 -7º12'10" m12s.6 12s.4 -10 -5 0 5 α Velocity (km/s) newspaper where alongside the text (J2000) there was a photograph of an astronaut doing a space walk. The Figure 2. Left panels: Absorption and emission by molecular gas towards the HII region in G24.78+0.08 A1, a massive caption was: “Astronomer working”. It star in process of formation with spectral type O9.5 and 20 solar masses. The upper panel shows the map of the integrated is true that we astronomers would like line emission of NH3. In the lower panel, the contours indicate the integrated line emission of CH3CN and the colours the CH3CN velocity gradient indicative of rotation. Right panels: Velocity field in the massive toroid G24.78+0.08 A1. The to take a closer look at the objects we upper panel shows the NH3 main line, the central panel shows the NH3 satellite line and the lower panel CH3CN. In the study, but for the time being I do not central panel one can clearly see that the absorption peak observed in the NH3 satellite line is shifted 2 km/s with respect to think anyone has gone that far! the stellar velocity, as indicated by the red line. This absorption shift towards positive velocities indicates that the gas, located between the star and the observer, is going away from the observer and moving towards the star, and therefore, infalling onto G24.78+0.08.
INFALL OF GAS AS THE FORMATION MECHANISM OF
STARS UP TO 20 TIMES MORE MASSIVE THAN THE SUN
M.T. BELTRÁN, R. CESARONI, C. CODELLA, L. TESTI,
R.S. FURUYA AND L. OLMI
2006, NATURE, 443, 427 133
Ricardo Hueso Alonso Departamento de Física Aplicada I Escuela Técnica Superior de Ingeniería Universidad del País Vasco, Bilbao
What was the problem you had surface. Agustín Sánchez-Lavega and storms in the atmospheres of the to face? I carried out the task of modelling giant planets Jupiter and Saturn, but In 2005, the European probe this phenomenon, trying to quantify accommodating them to the Huygens penetrated the atmosphere the amount of methane rain that can conditions of Titan’s atmosphere was of Saturn’s moon, Titan for the first fall on Titan’s surface. a great effort. Our model predicts time. This moon is the only natural that, under the right conditions, it is satellite with an atmosphere and has What was the solution to this possible to form in Titan convective a size comparable to that of Mercury. problem and the contribution this storms similar to the ones on Earth, At a vast distance from the Sun, paper made to the area of expertise but based on the condensation and 15,000 million kilometres, its in which it is framed? precipitation of methane. These temperature is so low, -180ºC, that In the study published in Nature we phenomena can produce a the methane in the atmosphere can made a three-dimensional numerical precipitation of about 50-200 litres condense forming clouds, which have model showing how a methane storm per square meter in a few hours, been regularly observed from the can be formed in Titan’s atmosphere. comparable to the intense storms Earth using large telescopes. The main challenge in this model which cause local flooding in Huygens found a landscape was to include how the small liquid summer and spring in the Iberian sculpted by watercourses and fluvial and frozen methane particles Peninsula. structures, a damp surface, although contained in the clouds are formed without liquids, and rounded stones and how they grow until producing Since the paper was published, have as the ones found on a dry riverbed. precipitation that reaches the surface. there been significant advances Both facts suggested that, The model itself was an adaptation in this specific area? occasionally, there are intense of previous works carried out by our Of course. Although the Huygens rainfalls of liquid methane on Titan’s team on the formation of water probe sent data on Titan’s surface for 135 Astronomy made in Spain
just a short period of time, the American Cassini probe is orbiting Saturn and its moons since 2004, providing new observations of Titan’s surface. In particular, its radar has found large lakes in both the northern and southern hemispheres. In addition, Titan is regularly monitored from the Earth using large telescopes and the seasonal cycle of its atmosphere is starting to be understood; an atmosphere governed by a slow rotation and the atmospheric cycle of methane. Several weeks ago we heard that some Figure 1. Titan observed by the Cassini probe. The atmosphere is covered by a permanent haze at high altitude that surface variations in the polar regions prevents us from directly observing the surface (left). At certain wavelengths (right) the haze becomes transparent and it is have been found after a period of possible to observe the surface and the formation of storms, in this case in the South Polar Region. intense storms observed from the Earth, one of the specific predictions of our model. Therefore, a large number of observations are consistent with our results and there has been an advance in global models of Titan’s atmosphere that take methane condensation into account.
Which are the main problems in this area of Astrophysics and what are the expected discoveries in the coming years? The frequency of the storms and their relation with the seasonal cycle of Titan 136 Spanish Astronomical Society
is not understood. The origin of atmospheric methane is not clear either, as it is known that methane is destroyed by solar ultraviolet radiation in the high atmosphere, recombining to form more complex hydrocarbons and dense layers of red haze, which hide the surface. Now we are starting to explore the global influence of storms on the surface using radar observations of Figure 2. Observations of Titan’s surface made with the Huygens probe; the watercourses and the round form of the regions which are similar to dunes over surface stones are clearly shown. The surface material is mainly water ice at very low temperature. a large part of the surface of Titan, and large lakes in the polar regions. However, it is not known if the lakes are deep or superficial, nor how much methane or ethane can be stored. Some of these mysteries could be solved with the new Cassini data but many will have to wait for the results of a new probe that has been proposed to the European and US space agencies that would be sent to explore Titan.
How did it influence your professional career? Have you continued in that line of work? Has it opened new perspectives or later did you dedicate yourself to other topics? This work was the one and only study to date that I have carried out 137 Astronomy made in Spain
on Titan’s atmosphere. Although we Do you have any anecdote related to started this line of research, later this paper’s gestation and publication we became part of a team that that you think is worth telling? analyses data from the European The paper was sent to publication after space mission Venus Express (since the summer of 2005, when my the year 2006) and therefore we have postdoctoral fellowship had just not been able to continue with our finished and I was unemployed and study of Titan. However, thanks to without the right to receive any the study outlined here, I have been unemployment compensation after consulted by European Space Agency nine years doing research with (ESA) and NASA committees about fellowships. I spent a few months living issues related to the design and out of my savings while we polished Figure 3. Simulation of a convective storm in Titan proposal of new Titan exploration the last details of this research work, with details of the precipitation and vertical velocities missions. I have also been the knowing that I had some results that developed in this vertical cloud. scientific referee of papers about I could not leave in a drawer. Later, I Titan’s atmosphere. On a more managed to return to the scientific general level, the publication of this research thanks to a Spanish “Ramón paper provided recognition of my y Cajal” contract. The impact of the research, which motivated me to paper about the methane storm on tackle new scientific objectives more Titan attracted significant interest in a enthusiastically. wide variety of publications and media.
METHANE STORMS ON SATURN’S MOON TITAN
R. HUESO AND A. SÁNCHEZ-LAVEGA
2006, NATURE, 442, 428
138 Rafael A. García Bustinduy Service d’Astrophysique (CEA-Saclay, Francia)
What was the problem you had that it has been impossible to detect properties in the Fourier space. In to face? them until now. this way we detected the periodicity The purpose of our study was to due to the bipolar modes (l=1) detect gravity-oscillation modes (also What was the solution to this comparing the results with the called g modes) in the Sun. Unlike problem and the contribution predictions (see Figure 1). This was acoustic modes (also called p modes) this paper made to the area of the first time that it was possible to that were detected at the end of the expertise in which it is framed? prove the existence of g modes in the sixties, g modes have remained In order to detect these weak waves, Sun. The work also permitted the undetected until now. These waves a French-Spanish consortium rotation rate of the Sun’s core to be are important because, unlike p developed the GOLF instrument constrained; it rotates on average modes, they propagate in the (Global Oscillations at Low about 4 to 5 times faster than the rest radiative zone of the Sun, especially Frequency) as part of the SoHO of the radiative zone. in its core. Therefore their detection (Solar and Heliospheric Observatory) will allow us to deepen our payload, launched on 2nd December Since the paper was published, have knowledge of the structural and 1995. Its main objective was, there been significant advances dynamic properties of this region, and still is, the detection of in this specific area? where nuclear reactions take place. low-frequency acoustic modes and g Due to the difficulty of measuring The problem we had to face was that modes. It has been necessary to such weak signals on the solar surface in the convective zone of the Sun collect data for 10 years in order and that there is no other instrument (the outer 30% of its structure) g to have enough sensitivity to detect able to reach such a high sensitivity, modes become evanescent, reaching those oscillations. the progress in this field is slow. the surface with velocities of the The detection of g modes was done At present we have extended the order of 1 mm/s or even lower, so indirectly, studying its asymptotic calculations using series of data 139 Astronomy made in Spain
10
GOLF 8
5.81 – 6 P.S. 4
2
0 MODEL
P.S. l=1, 2, 3
10 20 30 40 Period (min) Figure 2. Photo-montage representing the SoHO Figure 1. Periodogram (frequency spectrum) of data obtained with the GOLF experiment over a 10 year-period. satellite observing the Sun and a cross section of the The main peak corresponds to the periodicity of bipolar gravity modes. The same analysis is shown at the bottom Sun showing its convective zone (the outer 30% of of the figure but using theoretical frequencies for the above modes. The confidence level of the structure found is its structure) and its radiative zone, where gravity above 99.97%. modes propagate (represented by continuous lines). Image courtesy of IAC. obtained for 14 years (40% more resulting from the measurement Which are the main problems in this than in the original study) and we of the solar core rotation and the area of Astrophysics and what are have increased the precision of our verification of new opacity tables, the expected discoveries in the results. On the other hand, the which have been recently measured coming years? search of individual g modes and present certain inconsistencies From an observational point of view, continues and we are starting to with our results. In fact, not long you have to characterize the gravity obtain very promising results. ago, a new opacity table was modes (its amplitudes, frequencies, The most important advances have published which partially solves lifetimes, etc.) precisely and also come from theoretical implications the problem. measure the high-degree p modes 140 Spanish Astronomical Society
in order to study the radiative and able to measure all the things the several interviews. One of them was convective zones of the Sun in depth. instrument was designed and published in the Canary edition This knowledge will help us to constructed for. Obviously, we have of a national newspaper, and on their understand the structure and opened a door and the objective is to webpage they included a summary of dynamics of the internal regions go through it and go deep into this the interview, in which several of the Sun as well as the mechanisms field that has just been born for solar members of our team participated. that govern the solar magnetism and physicists. At the same time, the What we could not imagine was that its cycles that are very poorly techniques used to extract such weak this was the most-read paper during understood today. It is well known signals can be employed for the study the month of its publication and that these cycles affect the conditions of low signal-to-noise ratio pulsations because of this we were given a in space (with consequences, for in other stars. In fact, we were already commemorative statuette. No one example, in future manned flights to using these techniques with data from in the team could have imagined that Mars), produce disturbances in the CoRoT (Convection Rotation and people could show so much interest in satellite connections, and even affect Planetary Transits) and Kepler a scientific note on the Sun, to the the Earth’s climate. satellites. point of it being the most-read paper of the time. How did it influence your Do you have any anecdote related professional career? Have you to this paper’s gestation and continued in that line of work? Has publication that you think is worth TRACKING SOLAR GRAVITY MODES: THE DYNAMICS it opened new perspectives or later telling? OF THE SOLAR CORE did you dedicate yourself to other When this paper was published in R.A. GARCÍA, S. TURCK-CHIÈZE, S.J. JIMÉNEZ-REYES, topics? Science I was visiting the IAC J. BALLOT, P.L. PALLÉ, A. EFF-DARWICH, S. MATHUR After almost 15 years developing and (Instituto de Astrofísica de Canarias) AND J. PROVOST working with the GOLF instrument, and the mass media showed great 2007, SCIENCE, 316, 1591 it has been a great satisfaction to be interest in this issue and we gave
141
Marcos Cruz Rodríguez Departamento de Matemáticas, Estadística y Computación Universidad de Cantabria (Santander)
What was the problem you had What was the solution to this is necessary to obtain a definitive to face? problem and the contribution confirmation. In previous papers we analysed the this paper made to the area of Cosmic Microwave Background expertise in which it is framed? Since the paper was published, have radiation data provided by NASA’s After ruling out in several papers there been significant advances WMAP satellite, finding an anomaly, that the spot was due to Galactic in this specific area? namely a large cold spot of unknown contamination or instrumental noise, We have recently published a paper origin in the south Galactic we decided to check if the spot could comparing three hypotheses to hemisphere, with an angular radius have been created by a cosmic defect explain the origin of the spot. The of about 5 degrees. This spot was called a “texture”. The theory of probability that the spot had been detected by filtering the data with cosmic defects predicted a specific produced by a void or a large cluster a function called “Spherical Mexican pattern, amplitude and size for was very low and the hypothesis of Hat Wavelet”. The probability of the spot. Hence we performed a the cosmic texture continued to be observing such a spot according to Bayesian analysis in order to prove the most likely. Currently, we are the standard model was only about if the texture hypothesis could working on an extended all-sky 1% and the problem was that its explain the data. The result of this analysis in order to detect additional origin was unknown. analysis was that the spot was indeed textures predicted by the theory. consistent with the texture However, these textures are harder hypothesis. The first detection to detect since their angular size is of a cosmic defect would be a great smaller, and the anisotropies that are advance in our understanding of the not generated by textures have their early Universe and high-energy maximum power at scales between physics. However, additional analysis 1 or 2 degrees. 143 Astronomy made in Spain
Which are the main problems in this How did it influence your area of Astrophysics and what are professional career? Have you the expected discoveries in the continued in that line of work? Has coming years? it opened new perspectives or later In cosmology we have a standard did you dedicate yourself to other model, also called “concordant model”, topics? that explains reasonably well the We are currently finishing a paper observed Universe. However, the big which could confirm our discovery. problem of that model is that the My professional career has advanced Figure 1. Microwave Cosmic Background radiation nature of about 95% of the content considerably as I defended my thesis measured by NASA’s WMAP (left) and an azimuthal of the Universe is unknown. About some weeks after the publication projection of a 43º x 43º patch (A), centred at a prominent cold spot detected using spherical wavelets. 74% of the energy density of the of the paper and a year later, I signed We show through a Bayesian analysis that the most Universe is attributed to a “dark a contract for a position as Assistant acceptable hypothesis to explain the spot is a combination energy” of unknown origin, which Professor at the University of of two signals. One due to the cosmic defect, called would be the responsible for the Cantabria. texture (B) and a Gaussian signal due to the density expansion of the Universe. Most fluctuations of the early Universe (C). of the remaining energy is in the Do you have any anecdote related form of cold dark matter: non- to this paper’s gestation and baryonic and non-relativistic matter publication that you think is worth of unknown composition. Only 4% telling? of the energy in the Universe is I was lucky that the publication of accounted for by ordinary baryonic the paper in Science coincided with the matter. The big challenge of time when the journals Science and cosmology in the next few years Nature were bestowed the Prince of is to discover the nature of dark Asturias Award, so we were invited matter and dark energy. for a press conference in Oviedo,
144 Spanish Astronomical Society
where my grandparents live and I have good friends. The press conference was an interesting experience and I became “famous” for a short time, since I was interviewed by several radio stations and our work was mentioned in the national and international press.
Figure 2. Cosmic Microwave Background A COSMIC MICROWAVE BACKGROUND FEATURE radiation data taken by the WMAP (top) are CONSISTENT WITH A COSMIC TEXTURE filtered using the Spherical Mexican Hat Wavelet M. CRUZ, N. TUROK, P. VIELVA, E. MARTÍNEZ- at an angular scale of 5 degrees (right) to reduce noise and other contaminating signals, as well as GONZÁLEZ, AND M. HOBSON to amplify the signal to the selected scale. The 2007, SCIENCE, 318, 1612 filtered map (bottom) has less noise and it is possible to see a cold spot in the South Galactic Hemisphere which is more prominent that the others and could be the result of a cosmic effect.
145
Enric Pallé Bago Instituto de Astrofísica de Canarias (Tenerife)
What was the problem you reflected/emitted by the Earth, seen water, ozone, carbon dioxide and had to face? from an astronomical distance? What methane in our atmosphere. Anyone who has ever stopped to features can only be attributed to the Surprisingly, some gases of biological watch the starry sky has wondered existence of life? origin as methane (hardly present in if we are alone in the Universe. The our atmosphere), show much more past two decades have witnessed the What was the solution to this prominent features than those discovery of hundreds of extrasolar problem and the contribution this predicted by the models. A scientist planets (planets around other stars). paper made to the area of expertise who observed us from a distant star The recent advances in the detection in which it is framed? would not doubt to identify our and characterization of those The solution to this problem was planet as a place full of life. exoplanets makes us think that the to study the Earth’s transmission answer to that timeless question spectrum during a lunar eclipse. Since the paper was published, have is now a matter of time. During an eclipse, only the light that there been significant advances Although most of the planets passes through the terrestrial in this specific area? detected are gaseous giants, little by atmosphere can reach the darker area The study of exoplanets is an little we are very close to be able to of the shadow projected by the Earth incredibly dynamic field; in 2009 detect rocky planets similar to our over the Moon, the umbra. By there were more that two papers own Earth. When we will find them, studying the threshold light reflected every day. There are more than 500 the efforts will concentrate on onto the Moon we can recreate the planets detected and the new determining the likely presence observation of the Earth’s transit in discoveries of planets are being of life. More precisely, this was the front of the Sun. announced in scores of papers. So, problem we were considering: What With these observations we can there are indeed significant advances: are the characteristics of the light easily detect the presence of oxygen, Each time smaller and colder planets 147 Astronomy made in Spain
are discovered, closer to the habitability zone, and that little by little bring us closer to the detection of Earth-like planets. Regarding the characterization of the Earth’s atmosphere, it is still early to have more papers published about this issue, although our team is already preparing an extension of this Figure 1. The Moon during an eclipse from the study to other parts of the Canary Islands. Photograph courtesy of Daniel electromagnetic spectrum, especially López (IAC). to the infrared where there are many traces of the main greenhouse effect gases, and also to higher spectral resolutions.
Figure 2. An artist’s concept of the Earth, seen from Which are the main problems in this the Moon during a lunar eclipse. Photograph area of Astrophysics and what are courtesy of Gabriel Pérez (IAC). the expected discoveries in the coming years? Presently, the search of exoplanets and the existence of life in the Universe is encountering technical detection limits due to the enormous difference in brightness between these planets and their stars (the Sun is a thousand million times brighter than the Earth), and also the close proximity of both the planet and the star when they are observed at a large distance. 148 Spanish Astronomical Society
Some instruments designed today will be capable of detecting Earth- 1.0 a CH4 like planets; however, we will need 0.8 CH4 a quantitative jump to go from the H2O 0.6 H2O H2O detection of those planets to the H2O O2 0.4 characterisation of their atmospheres. O2 CO2 Relative Flux Relative The most promising technique at 0.2 3 O CO2 present is the so-called “differential 0.0 spectroscopy”, possible for those few 0.5 1.0 1.5 2.0 2.5 planets that, because of their orbital Wavelength ( m) geometry, cross in front of their stars. 1.0 In this sense, our study seems to b indicate that the search for life can 0.8 turn out to be a little easier than 0.6 it was expected. 0.4 Relative Flux Relative How did it influence your 0.2 professional career? Have you 0.0 0.5 1.0 1.5 2.0 2.5 continued in that line of work? Has it opened new perspectives or later Wavelength ( m) did you dedicate yourself to other topics? The truth is that it is still too early Figure 3. Top figure: The transmission spectrum of the Earth, where some of the major atmospheric constituents are marked. Bottom figure: A comparison between the Earth’s transmission (black) to say how this has influenced my and reflection (blue) spectra degenerated to low spectral resolution. professional career; it happened just a few months ago. The first time I published in Science probably helped me to get my present Ramón y Cajal contract. I would like to think that this new publication will help me to obtain a permanent position (even 149 Astronomy made in Spain
if we are in a time of crisis). What it Do you have any anecdote related to As soon as the Moon crossed the is clear is that I am planning to this paper’s gestation and publication limit from which we could observe it continue with this research line, that you think is worth telling? with the telescope, we started to work. because as well as being fascinating I remember that, due to the time There was no time to loose because it seems to have good medium and when it started, we could only lunar eclipses do not happen every day. long term future perspectives. observe the second half of the lunar The first results were already visible in a For the moment, the observations eclipse. At nightfall, the eclipse was raw analysis of the data done at the of the Earth and other planets of the already visible to the naked eye but telescope itself and that we discussed Solar System will be our benchmarks the Moon was still too low over the before going to bed. It happened to be in the search for life around other horizon to be accessible to the a great, exciting and enjoyable night. stars in our Galaxy. And despite what telescopes. Therefore, we sat down one could think, there are still many outdoors to take pictures and to aspects of our planet that remain to enjoy looking at this spectacular EARTH’S TRANSMISSION SPECTRUM FROM LUNAR ECLIPSE be characterised. phenomenon. OBSERVATIONS
E. PALLÉ, M.R. ZAPATERO-OSORIO, R. BARRENA, P.
MONTAÑÉS-RODRÍGUEZ AND E.L. MARTÍN.
2009, NATURE, 459, 814
150 María de Santos Lleó Centro Europeo de Astronomía Espacial (Madrid) Agencia Espacial Europea
What was the genesis and what are number of X-ray sources. It was then collides with material of the the objectives of the XMM-Newton understood that there was a need interstellar or intergalactic medium; observatory? to increase the sensitivity of the or in extreme gravity conditions, XMM-Newton is a European Space instruments and to introduce the as those taking place in the vicinity Agency (ESA) mission launched on capability to obtain spectra, i.e. to of black holes or neutron stars, very the 10th December 1999 to observe separate X-rays according to their often modified by intense magnetic the sky in X-rays. XMM-Newton’s energy or “colour”. In 1982, a fields. main challenge and objective was to proposal to build a satellite whose XMM-Newton’s increased put X-ray astronomy at the same “strengths” were precisely these two sensitivity to X-rays was achieved level as astronomy at other capabilities was formulated. In 1984, by using slightly curved cylindrical wavelengths. ESA approved the development of mirrors, which are capable of X-ray astronomy has a short the X-ray Multi-Mirror Mission as focusing photons that reach the history, since the Earth's atmosphere one of the four cornerstones of its interior at a very small incident absorbs all X-rays; its study is bound programme “Horizon 2000”, angle. Furthermore, many of those to space telescopes. It was not designed to bring ESA to the 21st cylindrical mirrors were placed one possible to detect X-rays coming century as one of the world’s leaders inside the other, as Russian dolls, in from the Sun until the first balloons in space research. order to increase the collecting area. or rockets were developed in the The XMM-Newton Space XMM-Newton carries three X-ray fifties. We had to wait until 1962 to Observatory was designed to help telescopes, containing each 58 see the first cosmic X-rays from an us to understand the Universe in mirrors of this type. The object other than the Sun. In the extreme temperature conditions, as spectroscopic power was achieved by seventies the first satellites were those generated when gas, accelerated designing the first reflection gratings launched, they detected an increasing to velocities close to that of light, which disperse X-ray photons at 151 Astronomy made in Spain
different angles according to their many discoveries made by XMM- Which are the main problems in this energy. An optical telescope was built Newton and Chandra that have area of Astrophysics and what are to complete the set, and it was transformed twenty-first century of the expected discoveries in the mounted parallel to the X-ray astronomy. coming years? telescopes, thus managing to collect The paper includes a sample list It is difficult to predict the main visible or ultraviolet light and X-rays of the most important discoveries, future discoveries and the impact at the same time. although it clearly states that this they may have. We are convinced list is neither objective nor complete that an important part of them will What are the contents of the review or, in other words, that it contains come from sky surveys, which are paper that youand your colleagues many of the several discoveries but increasingly deeper and cover larger have published in Nature? not all of them. The work covers and larger areas. We expect that in Before answering that question very different aspects: from X-ray the near future XMM-Newton and I would like to say that XMM- production mechanisms in comets Chandra will solve some critical Newton has a “cousin”, born almost or the influence of X-rays in planet issues ranging from the sub-nuclear at the same time, the NASA’s formation around young stars to composition of neutron stars to the Chandra satellite. Thanks to their the behaviour in of hot gas jets large-scale structure of the Universe. complementary properties, it has streaming from galaxies and Objects as diverse as the highest been possible to obtain very sharp impacting on the intergalactic layers of the Earth’s atmosphere or images and precisely measure the medium at high speed and thus the nuclei of the youngest galaxies, energy of cosmic X-rays. Thus, less regulating the growth of these still undetected because they are than 50 years after the first detection galaxies, of giant black holes in the extremely distant and therefore very of an extrasolar X-ray source, these galaxy cores and even of the large faint, will be studied. We are two observatories have achieved an scale structures of the Universe. In confident that a detailed census of increase in sensitivity comparable to the paper, we explain in detail some these objects over the history of the that obtained over the last 400 years of these discoveries. We also explain Universe will be done. The intention of optical astronomy, i.e. since how XMM-Newton and Chandra is to study the regions where stars are Galileo to the present day! have contributed and are still being formed, both in the Milky Way The paper published in Nature to contributing to our understanding and in younger distant galaxies, in celebrate the 10th anniversary of the of one of the most important order to understand what triggers the first observations made by these mysteries of astronomy today: the bursts of star formation and how satellites highlights some of the nature of dark matter and energy. these bursts modify the environment, 152 Spanish Astronomical Society
enriching it and injecting energy into the interstellar gas, or, in a similar way, how giant black holes in galaxy clusters inject energy into the intracluster gas. Surely, some of the discoveries will be done thanks to the cooperation with other telescopes, as for example ESA’s Herschel and Planck space missions, launched in May 2009, which will be essential for understanding obscured star formation, in the case of Herschel, or the nature of dark matter and energy, in the case of Planck.
Could you comment on the influence this project has had in your professional career? My professional career has completely changed since I started to work on the XMM-Newton Figure 1. Image of Messier 82, a galaxy with intense star formation observed with XMM-Newton in project. On the one side my work is ultraviolet, visible light, and X-rays; the latter are shown mainly in blue colours. Whereas the galactic plane is mainly seen in visible and ultraviolet light, with dark bands owing to dust and bright spots due to the process no longer mainly dedicated to of star formation, X-rays show two very hot gas cones bursting out from the galactic disk thanks to the boost astronomical research but more to given by the more massive stars when they explode as supernovas. This image perfectly illustrates the provide a service to astronomers, importance of having information in different wavelengths (visible, ultraviolet or X-rays), something which is something that despite reducing my possible with XMM-Newton. Courtesy: P. Rodríguez-Pascual and ESA. scientific “productivity” I have always considered very important. On the other hand, my own research has been increasingly 153 Astronomy made in Spain
centered on the analysis and interpretation of X-ray data. What I have kept from previous years working as an astronomer is my interest in active galactic nuclei and its connection with star formation; currently I am studying them mostly in the X-ray band, although I try to maintain an overall view, since they emit radiation in the entire electromagnetic spectral range.
Do you have any anecdote related to this paper’s gestation and publication or the events you have lived through in the 10 years of the XMM-Newton project? Regarding the paper I would like to stress the excellent collaboration with the co-authors who are part of the Chandra team. Together we have tried, and in my opinionsucceeded, to reveal the complementarity and excellence of both observatories. Regarding the XMM-Newton project, obviously, in more than ten Figure 2. The sky in X-rays: The image shows thousands of X-ray sources in an area of the sky which covers approximately 10 times the area of the full Moon, the XMM-COSMOS field. Red colours show the least energetic years all kinds of anecdotes have X-rays and blue colours show the more energetic ones, with green in the middle. Most of the approximately 2000 arisen. One of the main landmarks colour dots are active nuclei of distant galaxies, while the more than 100 regions, which appear as extended spots in any space mission is the launch: correspond to groups of galaxies or galaxy clusters. Courtesy: G.Hasinger, N.Cappelluti, XMM-COSMOS and in a few seconds, the past and the ESA collaboration. future of nearly a generation of 154 Spanish Astronomical Society
scientists is at a stake. We saw on a project as exciting as XMM- every day, making XMM-Newton the XMM-Newton launch live, Newton and I recognize that I have to be, and continue to be, a surrounded by colleagues who been a bit lucky because I was scientific success for many years suffered with nerves and enjoyed “in the right place at the right to come. the success with us. The next critical moment”. But undoubtedly the step came after a few days: opening most important thing has been the the mirror doors and collecting the privilege of working with people on THE FIRST DECADE OF SCIENCE WITH CHANDRA first data with the instruments, the project, with people that I value AND XMM-NEWTON the “first light”. It is amazing to and admire a lot, both professionally M. SANTOS-LLEÓ, N. SCHARTEL, H. TANANBAUM, W. realize how simple things as lifting and personally. The hardest thing is TUCKER AND M.C. WEISSKOPF a lid or opening a camera become the powerlessness I feel when I see 2009, NATURE, 462, 997 very complicated in space, them fearing for their future. When fortunately everything went well! a space project has been running The most critical event happened for a long time, its maintenance in October 2008. For several hours, becomes increasingly expensive for even days, we thought we had lost the space agencies, which have the satellite forever. It became “deaf”, amongst their main goals to develop “mute” and perhaps “blind”. It new technologies together with stopped sending signals and industry. Although scientists find answering to ours. Where was it? it very hard to understand the Why wasn't it answering? Luckily, reasoning based on immediate the problem could be solved as soon productivity gains, we have no as it was understood: A switch had choice but to try to achieve better got stuck and a very powerful signal and better results with fewer had to be sent to move it back to its resources. Despite the efforts done, correct position. The switch reacted jobs seem to be menaced by the to this signal and since then XMM- need to reduce expenses and even Newton continues to work perfectly, more so in times of crisis. That as before. insecurity is very hard. That is the On the personal side, I feel reason why I would like to thank privileged to have been able to work everyone who continues to work 155 The evolution of the expansion of a supernova remnant, detailed monitor- ings of gamma ray bursts, studies of the storms in Saturn and Jupiter, the first brown dwarf, the confirmation of the presence of black holes in bina- ry stars, models for novae and supernovae, the role of magnetic fields in the rotation pattern of galaxies, sunspots phenomena, the methane cycle in Titan, the impacts of volatile material on the Moon, the discovery of a spherical bubble around a stellar embryo, the description of the inter- galactic medium...
These are some of the results we present in ‘Astronomy made in Spain’, a project of the Spanish Astronomical Society (Sociedad Española de Astronomía, SEA) to commemorate the International Year of Astronomy 2009. This book is a collection of conversations with the Spanish astronomers who have published as first authors a paper —at least— in Nature or Science in the last 30 years. We would like this legacy paid homage to all Spanish astronomers, stimulated the new generations of students and composed a living history of discoveries told at first hand, without any intermediaries, by the people who made them possible.
Benjamín Montesinos Emilio J. Alfaro