Astronomical News DOI: 10.18727/0722-6691/5192

Report on the ESO Workshop The La Silla — From Inauguration to the Future held at Universidad de La Serena, , 25–29 March 2019

Ivo Saviane 1 gigantic steps over La Silla’s history, from History Bruno Leibundgut 1 single-­pixel detectors to the large arrays Linda Schmidtobreick 1 in use today. La Silla also experienced The workshop opened with welcome the transition from photographic plates addresses by the Rector of Universidad and simple electronic detectors to de La Serena (ULS) Nibaldo Avilés 1 ESO charge-coupled devices (CCDs) and Pizarro, by Mayor of the Higuera munici- today’s infrared arrays. La Silla also pality Yerko Galleguillos, and by President hosted the first large submillimetre dish in of the ESO Council Willy Benz. Also in This five-day workshop celebrated the the southern hemisphere. Different attendance were Vice-Dean of Research achievements of ESO’s first observa- operational schemes were tested at La and Development of ULS Eduardo Notte, tory, La Silla, on the occasion of its 50th Silla; some new adventures in running and Director of Research and Develop- anniversary. La Silla, officially inaugu- included remote observing ment of ULS Sergio Torres. rated on 25 March 1969, was the culmi- with the NTT and the Coudé Auxiliary nation of the vision of European astron- Telescope (CAT), and The historical context of astronomical omers to create a major observatory in the introduction of service observing at observatories in Chile was given by the southern hemisphere. In the follow- the NT T. Bárbara Silva from the Pontificia ing decades, La Silla served as a test- Universidad Católica de Chile. The earli- bed enabling the development of scien- The workshop celebrated the scientific, est astronomical site explorations by US tific, technical and operational expertise technological, operational and societal astronomers were carried out around the in the European astronomical commu- achievements over the past half century end of the 19th and the beginning of the nity, establishing communication — and charted the possible futures of 20th centuries and identified the Atacama channels with the public at large, and 4-metre-class telescopes in the era of Desert around Copiapó and north of working to increase interaction and col- extremely large telescopes. Many work- La Serena as potentially excellent laboration with the host country Chile shop participants had personally experi- sites for nighttime observations. The as well as with other astronomical facili- enced and participated in the history of International Geophysical Year in 1958 ties in the Andes mountains. Today, the . Their reports brought the Chilean sites to the attention La Silla continues to serve as a superb reminisced on the remarkable changes in of American astronomers again and site site hosting the ESO 3.6-metre and our understanding of the Universe, galax- explorations by Jürgen Stock — originally NTT telescopes, as well as a number of ies, stars and planets. At the same time, for the University of Chicago and later for community-led experiments. the workshop also attracted many young the Association of Universities for people who presented newer results and Research in (AURA) — identi- their visions for possible future uses of fied mountains around Vicuña as possible Introduction the La Silla telescopes. observatory sites. After the US National Science Foundation selected Cerro La Silla was the main observational The workshop took place in the special Tololo as their southern station, ESO also resource of European astronomers in the auditorium called El Pentagono on the became interested (through Stock’s for- southern hemisphere for the first three campus of the Universidad La Serena mer advisor Otto Heckmann, then ESO decades of ESO’s existence. The (ULS). The site overlooks the city of Director General). This was a rather observatory’s many telescopes, with a La Serena and the bay of Coquimbo, abrupt change from the original plan to range of different apertures, provided the which offered a spectacular setting for place the ESO observatory in southern tools to drive many discoveries. La Silla the workshop. The conference dinner Africa. Within a few years the La Silla was also the testbed for innovations in was at La Silla and included a tour of the mountain was selected and developed. telescope and instrument technology. observatory. Silva finished her presentation by display- The 2.2-metre Max-Planck-Gesellschaft ing a stamp showing the ESO 1-metre (MPG) telescope with its simple dome telescope, which was issued by the Chil- and, of course, the many new features Workshop overview ean Postal Office in 1973. implemented in the (NTT) in 1989 were critical for The workshop programme was built The relationship between Chile and ESO ESO’s path towards the Very Large around five topics: history, science, was explored by Claudio Melo, stressing Telescope (VLT). Many new instrument hosted projects, the future, and contrib- the friendly spirit that has guided this concepts were brought to the La Silla uted talks1. These topics were inter- relationship over the years. Chilean telescopes. The focal reducer spersed throughout the workshop so that astronomy has expanded tremendously spectrograph was first introduced with every day covered several aspects. over the past few decades and has made the ESO Faint Object Spectrograph and Hosted Projects — formerly called the country one of the leading nations in Camera (EFOSC) instruments and it was “National Telescopes” — are telescopes astronomical research. copied with the FOcal Reducer/low- and experiments installed on La Silla that dispersion Spectrograph (FORS) are operated by universities or consortia. Relations between the various observato- instrument on the VLT and at many other ries in Chile were described by Mario observatories. Infrared instruments made Hamuy and Leopoldo Infante. Hamuy has

36 The Messenger 179 – Quarter 1 | 2020 worked extensively at the Cerro Tololo of the Magellanic , the identifica- instruments were maintained and Inter-American Observatory and is a pro- tion of quasar absorbing systems as gal- improved over the years — a critical part fessor at the Universidad de Chile. A axies and the observation of ultra-­ of the successful operations. An inside leader of a Chilean Millenium project, he luminous galaxies. A bibliometric analysis view of the construction of the NTT was was recently head of the Chilean science for results published after 1996, when the given by Sergio Lopriore, who was the foundation (Comisión Nacional de ESO bibliographic records are complete, project engineer at the time, followed by Investigación Científica y Tecnológica, lists nearly 6680 published papers based Jason Spyromilio who recounted stories CONICYT), and as of October 2019 he is on data from La Silla telescopes until of the NTT Big Bang, bringing the NTT up the representative of the Association of 2018. Among the top results are the dis- to VLT standards. A further legacy of Universities for Research in Astronomy covery of the accelerated expansion of La Silla is the provision of new technolo- (AURA) in Chile. Leopoldo Infante is the the Universe, the discovery of the pecu- gies and Cesare Barbieri charted the director of the Las Campanas Observa- liar gamma-ray burst GRB 980425/ path from the NTT to the Telescopio tory. They stressed the friendly competi- SN 1998bw, the survey of G dwarf stars Nazionale Galileo (TNG) on La Palma. tion between the observatories, but also to map the solar neighbourhood, tracing Dietrich Baade reported on the impact of the assistance they have provided each the nature of the Galactic centre via the remote observing with the NTT, the 2.2- other, for example, the loan of the first orbits of stars, the connection between metre MPG telescope and the Coudé CCD detector from Cerro Tololo to host-star metallicity and the probability of Auxiliary Telescope (CAT). La Silla. hosting a planet, the high fraction of bina- rity among massive stars, and chemical Instrumentation development for La Silla The friendly challenge of the “observatory trends in stars in the thin and thick discs. underwent a long and arduous path. olympics” is held every few years, featur- Originally, many instruments followed ing competitions in various sports. Doug The historical development of the ESO American developments — in some Geisler reminded the audience of the joint telescopes was presented by Massimo cases copies of successful instruments workshops held by the observatories. Tarenghi, who had participated in the were purchased. Other instruments were Several memorable meetings could be commissioning of the 3.6-metre tele- temporarily installed at La Silla tele- reported (for example, the structure of the scope and led the construction of the scopes (visitor instruments) to obtain Milky Way, Galaxy Bulges, SN 1987A). 2.2-metre MPG telescope, the NTT and observations of the southern skies. A common concern of all observatories is the VLT. He gave an overview of the Sandro D’Odorico described how the light pollution; for example, the new illu- changing scientific and technical land- 2.2-metre MPG telescope and the NTT mination of the Panamericana near scapes and the technological advances required new instrumentation that paved La Frontera leads to light pollution at the which led ultimately to the VLT tele- the way for many VLT instruments. La Silla and Las Campanas observato- scopes. Michel Dennefeld gave a first- ries. Guillermo Blanc reported on the hand history of some early developments The prominent NTT instruments, EFOSC, efforts undertaken by the Oficina de of telescopes and instrumentation. The ESO Multi-Mode Instrument (EMMI), Proteccíon de la Calidad del Cielo del first large project on La Silla was the SUperb Seeing Imager (SUSI) and Son of Norte de Chile (OPCC), a collaboration Quick Blue Survey, which provided full ISAAC (SofI) were important stepping of the observatories and the Sociedad photographic coverage of the southern stones. High-­resolution spectroscopy has Chilena de Astronomía (SOCHIAS) to sky. The ESO Schmidt Telescope was become a strength of La Silla and Luca maintain the dark skies in northern Chile. specifically built for this purpose and Pasquini presented its history. The Coudé Sergio Ortolani gave an account of the Michael Naumann presented some of the Echelle Spectrometer (CES) for the 3.6- sky brightness above La Silla and its original plates. The objective-prism mode metre and the CAT was followed by the long-term evolution. He noted that of the ESO Schmidt had been used in Cassegrain Echelle Spectrograph La Silla has a very dark sky at the zenith spectroscopic surveys, for example the (CASPEC) on the 3.6-metre, which was and a long-term pattern of cover- Hamburg–­ESO Survey, to search for the only high-­resolution spectrograph age. About 70% of nights on La Silla are white dwarfs and quasars. Ana Cristina with polarimetric capabilities, as photometric. Armond presented new plans to take up described by Gautier Mathys. Another objective-prism spectroscopy with the high-resolution spectrograph, the Fibre- Jorge Melnick began the scientific dis- SOuthern Astrophysical Research (SOAR) fed Extended Range Optical Spectro- cussions by offering his list of the top ten telescope. graph (FEROS), was initially mounted at results obtained with La Silla telescopes. the ESO 1.5-metre telescope and then He first demonstrated the ever-increasing Gerardo Ihle led us on a journey down moved to MPG 2.2-metre. HARPS on the demand for La Silla telescopes by show- memory lane, sharing his thoughts about 3.6-metre remains a unique facility for ing the surge in the number of proposals the development of the Mechanical measuring accurate radial velocities. from fewer than 100 at the beginning to Engineering Group on La Silla; the high- nearly 600 proposals for Period 54, light was the design, manufacture, and Christian Gouiffes followed the various before the start of the NTT Big Bang commissioning of a new M2 unit for the attempts at high-time-resolution photom- (1995–96) and the introduction of the VLT 3.6-metre telescope, which fixed its etry undertaken at La Silla and gave a (1999, Period 63). Results from the early image quality issues some 30 years after very nice account of the ESO rejection of years include many stellar topics, studies first light. The La Silla telescopes and a putative pulsar in SN 1987A found at

The Messenger 179 – Quarter 1 | 2020 37 Astronomical News Saviane I. et al., Report on the ESO Workshop “The La Silla Observatory”

another observatory. New instruments will equip the 3.6-metre telescope (the Near Infra-Red Planet Searcher, NIRPS) and NTT (Son Of X-shooter, SOXS) in connection with large dedications of observing time for powerful surveys of the next decade. Colin Snodgrass also pre- sented a proposal for a high-­resolution imager (GravityCAM) for the NTT.

Many infrared instruments debuted at La Silla and Ulli Käufl gave an overview of infrared instrumentation on La Silla over four decades. The first instruments were bolometers, followed by the first spectro- graphs (IRSPECs) and cameras (IRACs) and the extension into the thermal infra- red with the Thermal Infrared MultiMode Instrument (TIMMI) instruments. The most prominent TIMMI result came from following the impact of Shoemaker-Levy 9 on . and orbital parameters) were derived. The Figure 1. Conference participants at sunset on Experiments occasionally came to oldest stars reflect the chemical abun- La Silla. La Silla, for example the millimetre-wave dance in the early Universe before chemi- heterodyne receivers brought to the ESO cal enrichment took place. essentially founding the field of 1.5-metre and later the 3.6-metre tele- research as it is conducted today. The scopes to measure CO(2–1). Thijs de Monique Spite gave a historical introduc- dedication of a large fraction of observing Graauw took part in these early observa- tion to the recognition of metal-poor stars time over nearly two decades, coupled tions and recounted how they eventually and their importance in understanding with the exquisite wavelength accuracy led to ESO’s hosting the Swedish–ESO chemical enrichment. She described the of HARPS, has contributed to the field’s Submillimeter Telescope (SEST) on contributions by La Silla telescopes, in progressing from the discovery of La Silla. Lars-Åke Nyman presented the particular the searches by the Hamburg–­ gaseous giant planets to finding rocky many successes of the SEST during its ESO objective-­prism survey with the ESO super earths and uncovering several 15 years of operation and its important Schmidt telescope and follow-­­up high-­ planetary systems. Radial velocity role as precursor to the current resolution spectroscopy. These studies searches have been performed over submillimetre telescopes in Chile. were continued with one of the first VLT many years with the (hosted) Euler tele- Large Programmes on the “first stars” scope and Stéphane Udry described with the UV-Visual Echelle Spectrograph the many successes. By now, planets Science (UVES). The importance of stellar binarity with orbits of longer than 10 000 days (and multiplicity) was described by Hans (> 27 years!) have been found. Francesco Birgitta Nordstrom presented one of the Zinnecker. The ever-improving image Pepe charted the successes of HARPS most successful programmes that used quality led to the “breaking up” of the most and how it is now part of a suite of instru- La Silla telescopes, showing how the massive known stars into smaller constitu- ments used to study . The Geneva–Copenhagen Survey of the Solar ents and the La Silla telescopes played an prospects for this field are bright, with Neighbourhood changed our views of the important role, particularly in resolving the NIRPS on the 3.6-metre opening up the Milky Way. This project, which lasted for stars in the . Similarly, possibility to search for planets around over 15 years and required more than the young stars in the Orion star forma- low-mass stars, as presented by Francois 1000 observing nights, collected the tion region are mostly binaries, and it has Bouchy. Thierry Forveille (on behalf of space motions of over 14 000 F- and since become clear that nearly all mas- Xavier Bonfils) showed how small tele- G-type stars within ~ 100 pc (complete sive stars are in close binaries. scope projects, like the three robotic ExTrA out to 40 pc) of the Sun. Distances, hosted telescopes on La Silla, can be absolute magnitudes, effective tempera- , the guiding light behind used to search for transiting planets tures, metallicity, proper motions (from the High Accuracy Radial velocity Planet around M dwarfs and to study their the HIPPARCOS satellite) and radial Searcher (HARPS), presented the evolu- atmospheres. A similar project focusing velocities for all the stars were deter- tion of exoplanet discoveries with this on the brightest stars is the Multi-­site mined. About a third (34%) of the stars instrument. Later in the year, Michel All-Sky CAmeRA (MASCARA), which is are binaries. From these observed values, received (together with Didier Queloz) half run by Ignas Snellen. several quantities (ages, space motion of the 2019 Nobel Prize in Physics for

38 The Messenger 179 – Quarter 1 | 2020 André Maeder presented La Silla’s contri- ray bursts (GRBs). PESSTO and its suc- the Danish 1.5-metre is fully dedicated to butions to stellar astrophysics. HARPS cessor ePESSTO were presented by and is jointly operated by a has become the instrument of choice for Rubina Kotak. PESSTO followed a long Danish and Czech consortium. It is regu- determining stellar abundances and col- tradition of programmes studying super- larly used for exoplanet transit observa- lecting the time series spectra required novae at La Silla. Masimo Turatto was a tions, and also discovered the rings for asteroseismology. Combined with key member of those projects and sum- around the asteroid Chariklo via theoretical progress on modelling rotating marised the many results on supernovae . stars, our understanding of the interiors obtained with La Silla telescopes. A spe- of stars has increased dramatically. The cial aspect he emphasised is the impor- One of the first robotic telescopes was observations of globular clusters have tant role of such programmes in forming TAROT (Télescope à Action Rapide pour always been central to stellar evolution European collaborations. les Objets Transitoires — Rapid Action studies and Georges Meylan summarised Telescope for Transient Objects), designed what is known about cluster kinematics SN 1987A has a special place in La Silla’s to hunt for GRBs; this project was pre- and dynamics. The line of instruments history. The observations and unique sented by Michel Boër. The REM (Rapid from CORAVEL (Danish 1.5-metre tele- contributions by the La Silla telescopes Eye Mount) was scope) to CORALIE (Euler 1-metre tele- were summarised by Patrice Bouchet. in­stalled in 2003 to follow GRBs photo- scope) and to HARPS at the 3.6-metre The early indication of circumstellar mate- metrically in the infrared. Emilio Molinari with ever increasing radial velocity accu- rial stemmed from NTT observations and presented the history and successes of racy was leading the way to resolved was later confirmed by HST. The infrared this telescope. Today, REM focuses on kinematics and dynamics in globular observations of SN 1987A were led by time-domain astronomy (mostly follow-up clusters. ESO facilities and they provided impor- of fast triggers like GRBs and kilonovae) tant results, including monitoring the early but also exoplanet transits and space Frank Eisenhauer summarised 28 years dust formation and freeze-out at late debris. The TRAnsiting Planets and of observations of the Galactic centre times. An unbroken observational record PlanetesImals Small Telescope (TRAPPIST) from La Silla and Paranal, culminating of SN 1987A exists until today and contin- is a robotic 60-cm telescope and was in the spectacular observations of the ues with the inclusion of VLT and ALMA. presented by Emanuel Jehin. TRAPPIST-­ effects of strong gravity close to the South has now operated for 10 years and supermassive black hole at the centre of The Galactic bulge has been a favourite is also used for educational purposes in the Milky Way. La Silla telescopes were target for La Silla telescopes. Beatriz university courses. Its biggest success so among the first to employ speckle imag- Barbuy reported on the latest results. far is the discovery of a planetary system ing (for example, the SHARP camera) and The old population of the bulge has been consisting of seven transiting Earth-like adaptive-optics-assisted observations of confirmed and a clear signal of enrich- planets around an ultra-cool dwarf the stellar population in the densest part ment of alpha elements by core-collapse (2MASS J23062928-0502285, now better of our Milky Way. Tracing the orbit of the supernovae is found. The abundances in known as TRAPPIST-1). This is one of the star S2 around the black hole com- the bulge are comparable to those in the richest and best studied planetary sys- menced at La Silla. thick disc, while the oldest globular clus- tems so far. ters are confined to the bar in the inner Cataclysmic variables and the current Galaxy. After many years of time being offered status of white dwarf observations were to the ESO community on the MPG presented by Linda Schmidtobreick and 2.2-metre telescope, the telescope has Tom Marsh, respectively. La Silla tele- Hosted telescopes now become a hosted telescope on scopes have contributed to these fields La Silla and is operated by the MPG. via numerous Target of Opportunity (ToO) La Silla has hosted non-ESO (“national”) The exciting prospects of the BlackGEM and monitoring programmes. UltraCAM is telescopes for many years. Some of telescope array were presented by Paul a visitor instrument which provides these operated on a mixed model with Groot. The three 60-cm telescopes are unique high-time-resolution capabilities observing time available to the ESO com- mainly set up to observe the electromag- helpful for many of the white dwarf stud- munity. The Danish 1.5-metre telescope netic counterparts of gravitational wave ies. One of the primary goals of SOXS is began operating in 1978 and Michael events. The installation is well under way the monitoring of variable sources. Pietro Andersen gave an overview of its scien- and first light was obtained in January Schipani presented the concept and tific achievements as well as future plans. 2020. Another future telescope is the goals of SOXS. The wide-band spectro- This telescope was also one of the first ESA TestBed Telescope (TBT), a 1-metre scopic coverage and the large allocation on La Silla to use a CCD detector. This telescope to continuously monitor the sky of observing time at the NTT will enable setup was used by a Danish team to dis- for space debris and near-Earth objects. surveys of transient phenomena on cover the first distant supernovae, which It will be a precursor to the ESA Near an unprecedented scale. SOXS follows opened up the possibility of observing Earth Object Survey Telescope (NEOSTel) in the footsteps of the Public ESO the cosmic expansion rate beyond the to survey the sky continuously in order to Spectroscopic Survey of Transient local Universe. In addition, the telescope detect fast-moving objects. Objects (PESSTO), which has provided has also made important observations of new insights into supernovae and gamma-­ GRBs and lensing of exoplanets. Today

The Messenger 179 – Quarter 1 | 2020 39 Astronomical News Saviane I. et al., Report on the ESO Workshop “The La Silla Observatory”

The first La Silla telescope, the 1-metre not require 8-metre- or 40-metre-class tem as offered to its community. The photometric telescope, was installed in telescopes. The time domain will become La Silla observatory offers a prime site, 1966 (even before the official inauguration a major area for 4-metre-class telescopes significant instrumental capabilities and a of the observatory) and, as presented by in the future. Many science cases requir- versatile operations model. Fifty years Moni Bidin, since it ceased ESO opera- ing long-term monitoring (for example, after its inauguration the La Silla Observa- tions it has been used by Bochum exoplanets, transient phenomena) will be tory is still going strong and the promise of University and the Universidad Católica best served with ESO’s 4-metre-class new scientific discoveries continues. del Norte. A new high-resolution spectro- tele­scopes. The support role of some graph (FIDEOS) built by the Pontificia of these telescopes to complement mis- Acknowledgements Universidad Católica de Santiago was sions such as PLATO was also stressed installed in 2016 and is used for several times. The organisers would like to thank the University of exoplanet work. An important aspect of La Serena for the support provided for this workshop. small (privately-run) telescopes is the training of astronomers at the start of Demographics Links their careers. Alessandro Ederoclite described the potential use of small tele- The workshop was attended by 74 regis- 1 The programme with links to the individual scopes in the future. Throughout its his- tered participants (see Figure 1), with only ­presentations:­ https://www.eso.org/sci/ meetings/2019/lasilla2019/program.html tory, La Silla has often served as the first nine female participants (just under 12%). introduction to professional astronomy for This was lower than the ratio of women early career researchers, and more to men in the Science Organising recently this role has been boosted as Committee (3:9). There were only five the site of several astronomy training women among the 41 invited speakers schools. Bruno Dias gave an account (also 12%). Of the 18 contributed talks of the most recent school and Michel only 2 were given by female speakers. Dennefeld placed this into the wider con- It should, however, be noted that more text of the Network of European Obser- than half of the participating women were vatories in the North (NEON) schools. invited speakers. These numbers reflect in part the demographics during the early history of astronomy in Europe. Future

The workshop ended with a general dis- Summary cussion of the future of La Silla. Andreas Kaufer gave an overview of the plans for The La Silla Observatory has participated the next few years to set the stage of the in most of the revolutions in astronomy discussion. Central to these are the oper- over the past 50 years. The synergies ation of the 3.6-metre telescope and the with other observatories, in particular NTT, which will be equipped with new with space-based observations in the instruments that will be dedicated ultraviolet, in X-rays and in gamma rays, to specific science topics. Once the have been highly beneficial. The develop- 3.6-metre telescope has been equipped ment of state-of-the-art instrumentation with HARPS and NIRPS, it will become and the improvement in detector technol- the primary facility for high-precision ogies reduced the need for larger tele- radial velocity studies in the optical and scopes for several decades. A further the near-infrared. SOXS on the NTT will strength of La Silla programmes was (and focus mainly on the spectroscopy of tran- still is) the large instrument complement sient objects and will be the primary and the possibility to execute long-term spectroscopic follow-up facility for future programmes — in some cases lasting surveys. A third component is the hosting decades. La Silla has been Europe’s flag- of telescopes run by external consortia to ship facility for three decades and has enable access to the southern hemi- continued to produce exciting science sphere at an excellent site. results from surveys during the VLT era. In the future, it will focus its facilities even During the discussions a number of more on long-term and survey projects, points were made. La Silla telescopes which are impossible at larger telescopes already complement the current flagship given the demands on their time. facilities, VLT and ALMA, and will become workhorses for massive surveys of the La Silla telescopes cover an important brighter sky, targeting all objects that do part of ESO’s integrated observing sys-

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