DOCSLIB.ORG

From ESPRESSO to PLATO: Detecting and Characterizing Earth-Like Planets in the Presence of Stellar Noise

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
From ESPRESSO to PLATO: Detecting and Characterizing Earth-Like Planets in the Presence of Stellar Noise From ESPRESSO to PLATO: detecting and characterizing Earth-like planets in the presence of stellar noise Tese de Doutouramento Luisa Maria Serrano Departamento de Fisica e Astronomia do Porto, Faculdade de Ciências da Universidade do Porto Orientador: Nuno Cardoso Santos, Co-Orientadora: Susana Cristina Cabral Barros March 2020 Dedication This Ph.D. thesis is the result of 4 years of work, stress, anxiety, but, over all, fun, curiosity and desire of exploring the most hidden scientific discoveries deserved by Astrophysics. Working in Exoplanets was the beginning of the realization of a life-lasting dream, it has allowed me to enter an extremely active and productive group. For this reason my thanks go, first of all, to the ’boss’ and my Ph.D. supervisor, Nuno Santos. He allowed me to be here and introduced me in this world, a distant mirage for the master student from a university where there was no exoplanets thematic line. I also have to thank him for his humanity, not a common quality among professors. The second thank goes to Susana, who was always there for me when I had issues, not necessarily scientific ones. I finally have to thank Mahmoud; heis not listed as supervisor here, but he guided me, teaching me how to do research and giving me precious life lessons, which made me growing. There is also a long series of people I am thankful to, for rendering this years extremely interesting and sustaining me in the deepest moments. My first thought goes to my parents: they were thousands of kilometers far away from me, though they never left me alone and they listened to my complaints, joy, sadness...everything. Thank you, without your sustain I would not be here writing this thesis. I also have to thank my historical friends, Federico and Silvia. I went away from Trieste, still they kept on being always present and getting updated with my life. A special thank goes to other Ph.D. students and researchers who shared with me nice moments: Akin, Raquel, Solene, João, Fatima and Elisa more than everybody, but I should mention a long list of people here. For this reason, I will just say: thank you CAUP, for the friendly environment you offered me. Thank you Nuno, Júlia and Jorge for sharing with me my other passion, archery, my best stress relies. And thanks to Alessia, Nicoló, Irene and all those, who in the last 2 years ’stucked with me until the very end’. Without all of you these years would have been completely different and, probably, less interesting. Finally, I have to thank someone who entered my life silently and slowly, becoming unexpectedly important to me. Zé, you were there as a friend, you are still here as my love, and you sustained me through these last months of thesis. I hope our future is going to be bright. ii Abstract The search for extra-solar planets dates back to the mid 20th century, when the Doppler effect was proposed as a possible detection method (Struve 1952). As the time passed, a deeper understanding of the stellar physics and its manifestation and the spectroscopic improvements, allowed the discovery of the first exoplanet, by Mayor & Queloz (1995). Their work represented a fundamental milestone for the field, which grew faster as new detection methods were adopted and the instrumental precision improved. Nowadays, this field, among the other objectives, heads towards a precise characterization of exoplanets and their atmospheres and the identification of an Earth-twin. Reaching these aims can only be possible by adopting very precise instruments and accounting for several sources of stellar noise. In this thesis, we specifically analyze the measurability with the current and future instruments oftwo planetary parameters, the albedo and the spin-orbit angle. The albedo of an exoplanet represents the fraction of stellar light reflected by the planetary atmo- sphere. Since reflection depends on the structure and composition of the layers crossed by photons, knowing the albedo helps to probe the presence of clouds and specific molecules in the atmosphere. Measuring this parameter is challenging and it requires the detection of the reflected light through opti- cal photometric observations. This detection is possible in the context of phase curve analysis. A phase curve is the flux variation from the target star and its orbiting planets as a function of time. Itinvolves, in optical wavelengths, the primary transit, the secondary eclipse and 3 more effects, the beaming effect, the ellipsoidal modulation and the reflected light component. While the beaming and ellipsoidal areneg- ligible, the reflected light might dominate the out-of-transit flux if there were no additional noise.The presence of instrumental noise and stellar activity may cause difficulties and obstacles in the detection of the planetary signal, even accounting for a precise knowledge of the planetary properties derivable from the transit feature. While the instrumental noise can be reduced with better instruments or even by binning the data, the stellar activity cannot be removed, especially in the context of a space telescope, such as CHEOPS, which will offer a limited time-span for observations (20 days). In our work, we explored how the stellar activity could limit the detection of the planetary albedo, accounting for an increasing observational time and imposing CHEOPS precision as instrumental noise. In detail, we built mock light curves, including a realistic stellar activity pattern, the reflected light component of the planet and white noise, averagely on the level of CHEOPS noise for different stellar magnitudes. Afterwards, we fit our simulations with the aim of recovering the reflected light component and assuming the activity patterns could be modeled with a Gaussian process. The main conclusion of such analysis was that at least one full stellar rotation is necessary to retrieve the planetary albedo. iii This result, independent of the level of noise, is a consequence of the adopted methodology to model the stellar activity, the Gaussian process, which needs to detect the full stellar rotation to describe the activity pattern. We found as well that, for a 6.5 magnitude star and accounting for CHEOPS noise level, it is possible to detect the planetary albedo up to a lower limit of RP = 0:03R∗. These results can represent a starting point for phase curve analysis not only with CHEOPS, but also with future photometric missions, such as PLATO and TESS. They also show that detecting the albedo for Earth- like planets will only be possible with an increased photometric precision and long observations, as they will be offered by PLATO. The projected spin-orbit angle is the angle between the planetary orbit and the stellar rotational axis. It can be measured through the Rossiter-McLaughlin (RM) effect, the radial velocity signal generated when a planet transits a rotating star. Stars rotate differentially and this affects the shape and amplitude of the RM signal, on a level that can no longer be ignored with precise spectrographs. Highly misaligned planets provide a unique opportunity to probe stellar differential rotation via the RM effect, asthey cross several stellar latitudes. In this sense, WASP-7, and its hot Jupiter with a projected misalignment of ∼ 90◦, is one of the most promising targets. Although Albrecht et al. (2012a) measured the RM of WASP-7b, they found no strong detection of the stellar differential rotation, which suggests us the possibility of an imprecise measurement of the spin-orbit misalignment as well. For this reason, we decided to explore the main hurdles which prevented the determination of WASP-7 differential rotation, adopting the tool SOAP3.0, updated in way it accounted as well for non-rigid stellar rotation. Furthermore, we investigated whether the adoption of the new generation spectrographs, like ESPRESSO, would solve these issues. We finally assessed how instrumental and stellar noise influence this effect and the derived geometry of the system. We found that, for WASP-7, the whitenoise represents an important hurdle in the detection of the stellar differential rotation, and that a precision of at least 2 m s−1 or better is essential. However, we noticed that the past observations of WASP-7b show unusually high residuals, which cannot be justified with any of the additional stellar noise sources explored in our analysis and, thus, they require further exploration. Such exploration would be well suited to the ESPRESSO spectrograph for WASP-7-like systems, as it will provide the radial velocity precision necessary to disentangle the instrumental and stellar noise sources. Unluckily this kind of measurement in the case of Earth-like planets appears to be a quite far achievement. As an overall result we can conclude that the detailed description of the planet, especially with the current and new instruments, is only possible when properly accounting for the stellar noise sources. Moreover, the presence of a planet can help as well in understanding better certain stellar properties, as it is the case of stellar rotational pattern explored in our works. With this thesis, we can thus strongly iv stress the importance of exoplanets in the frame of stellar analysis and vice-versa. v Resumo A pesquisa por exoplanetas foi pela primeira vez considera no século 20, quando o efeito Dopler foi proposto como um possível método de detecção (Struve 1952). Assim que o nosso conhecimento de Física estelar evoluiu e o campo da espectroscopia avançou o suficiente, foi possível descobrir o primeiro exoplaneta, por Mayor & Queloz (1995). Esta descoberta marcou o nascer do campo de exoplanetas, que cresceu cada vez mais rápido assim que novos métodos de detecção e análise foram descobertos e a precisão instrumental melhorou. Hoje em dia, um dos vários objectivos deste campo consiste em realizar caracterizações precisas dos exoplanetas e suas atmosferas, assim como a identificação de planeta gémeo da Terra.
Load more

Recommended publications
  • Lurking in the Shadows: Wide-Separation Gas Giants As Tracers of Planet Formation
    Lurking in the Shadows: Wide-Separation Gas Giants as Tracers of Planet Formation Thesis by Marta Levesque Bryan In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy CALIFORNIA INSTITUTE OF TECHNOLOGY Pasadena, California 2018 Defended May 1, 2018 ii © 2018 Marta Levesque Bryan ORCID: [0000-0002-6076-5967] All rights reserved iii ACKNOWLEDGEMENTS First and foremost I would like to thank Heather Knutson, who I had the great privilege of working with as my thesis advisor. Her encouragement, guidance, and perspective helped me navigate many a challenging problem, and my conversations with her were a consistent source of positivity and learning throughout my time at Caltech. I leave graduate school a better scientist and person for having her as a role model. Heather fostered a wonderfully positive and supportive environment for her students, giving us the space to explore and grow - I could not have asked for a better advisor or research experience. I would also like to thank Konstantin Batygin for enthusiastic and illuminating discussions that always left me more excited to explore the result at hand. Thank you as well to Dimitri Mawet for providing both expertise and contagious optimism for some of my latest direct imaging endeavors. Thank you to the rest of my thesis committee, namely Geoff Blake, Evan Kirby, and Chuck Steidel for their support, helpful conversations, and insightful questions. I am grateful to have had the opportunity to collaborate with Brendan Bowler. His talk at Caltech my second year of graduate school introduced me to an unexpected population of massive wide-separation planetary-mass companions, and lead to a long-running collaboration from which several of my thesis projects were born.
    [Show full text]
  • Where Are the Distant Worlds? Star Maps
    W here Are the Distant Worlds? Star Maps Abo ut the Activity Whe re are the distant worlds in the night sky? Use a star map to find constellations and to identify stars with extrasolar planets. (Northern Hemisphere only, naked eye) Topics Covered • How to find Constellations • Where we have found planets around other stars Participants Adults, teens, families with children 8 years and up If a school/youth group, 10 years and older 1 to 4 participants per map Materials Needed Location and Timing • Current month's Star Map for the Use this activity at a star party on a public (included) dark, clear night. Timing depends only • At least one set Planetary on how long you want to observe. Postcards with Key (included) • A small (red) flashlight • (Optional) Print list of Visible Stars with Planets (included) Included in This Packet Page Detailed Activity Description 2 Helpful Hints 4 Background Information 5 Planetary Postcards 7 Key Planetary Postcards 9 Star Maps 20 Visible Stars With Planets 33 © 2008 Astronomical Society of the Pacific www.astrosociety.org Copies for educational purposes are permitted. Additional astronomy activities can be found here: http://nightsky.jpl.nasa.gov Detailed Activity Description Leader’s Role Participants’ Roles (Anticipated) Introduction: To Ask: Who has heard that scientists have found planets around stars other than our own Sun? How many of these stars might you think have been found? Anyone ever see a star that has planets around it? (our own Sun, some may know of other stars) We can’t see the planets around other stars, but we can see the star.
    [Show full text]
  • Durham E-Theses
    Durham E-Theses First visibility of the lunar crescent and other problems in historical astronomy. Fatoohi, Louay J. How to cite: Fatoohi, Louay J. (1998) First visibility of the lunar crescent and other problems in historical astronomy., Durham theses, Durham University. Available at Durham E-Theses Online: http://etheses.dur.ac.uk/996/ Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in Durham E-Theses • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders. Please consult the full Durham E-Theses policy for further details. Academic Support Oce, Durham University, University Oce, Old Elvet, Durham DH1 3HP e-mail: [email protected] Tel: +44 0191 334 6107 http://etheses.dur.ac.uk me91 In the name of Allah, the Gracious, the Merciful >° 9 43'' 0' eji e' e e> igo4 U61 J CO J: lic 6..ý v Lo ý , ý.,, "ý J ýs ýºý. ur ý,r11 Lýi is' ý9r ZU LZJE rju No disaster can befall on the earth or in your souls but it is in a book before We bring it into being; that is easy for Allah. In order that you may not grieve for what has escaped you, nor be exultant at what He has given you; and Allah does not love any prideful boaster.
    [Show full text]
  • A Hot Subdwarf-White Dwarf Super-Chandrasekhar Candidate
    A hot subdwarf–white dwarf super-Chandrasekhar candidate supernova Ia progenitor Ingrid Pelisoli1,2*, P. Neunteufel3, S. Geier1, T. Kupfer4,5, U. Heber6, A. Irrgang6, D. Schneider6, A. Bastian1, J. van Roestel7, V. Schaffenroth1, and B. N. Barlow8 1Institut fur¨ Physik und Astronomie, Universitat¨ Potsdam, Haus 28, Karl-Liebknecht-Str. 24/25, D-14476 Potsdam-Golm, Germany 2Department of Physics, University of Warwick, Coventry, CV4 7AL, UK 3Max Planck Institut fur¨ Astrophysik, Karl-Schwarzschild-Straße 1, 85748 Garching bei Munchen¨ 4Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106, USA 5Texas Tech University, Department of Physics & Astronomy, Box 41051, 79409, Lubbock, TX, USA 6Dr. Karl Remeis-Observatory & ECAP, Astronomical Institute, Friedrich-Alexander University Erlangen-Nuremberg (FAU), Sternwartstr. 7, 96049 Bamberg, Germany 7Division of Physics, Mathematics and Astronomy, California Institute of Technology, Pasadena, CA 91125, USA 8Department of Physics and Astronomy, High Point University, High Point, NC 27268, USA *[email protected] ABSTRACT Supernova Ia are bright explosive events that can be used to estimate cosmological distances, allowing us to study the expansion of the Universe. They are understood to result from a thermonuclear detonation in a white dwarf that formed from the exhausted core of a star more massive than the Sun. However, the possible progenitor channels leading to an explosion are a long-standing debate, limiting the precision and accuracy of supernova Ia as distance indicators. Here we present HD 265435, a binary system with an orbital period of less than a hundred minutes, consisting of a white dwarf and a hot subdwarf — a stripped core-helium burning star.
    [Show full text]
  • Naming the Extrasolar Planets
    Naming the extrasolar planets W. Lyra Max Planck Institute for Astronomy, K¨onigstuhl 17, 69177, Heidelberg, Germany [email protected] Abstract and OGLE-TR-182 b, which does not help educators convey the message that these planets are quite similar to Jupiter. Extrasolar planets are not named and are referred to only In stark contrast, the sentence“planet Apollo is a gas giant by their assigned scientific designation. The reason given like Jupiter” is heavily - yet invisibly - coated with Coper- by the IAU to not name the planets is that it is consid- nicanism. ered impractical as planets are expected to be common. I One reason given by the IAU for not considering naming advance some reasons as to why this logic is flawed, and sug- the extrasolar planets is that it is a task deemed impractical. gest names for the 403 extrasolar planet candidates known One source is quoted as having said “if planets are found to as of Oct 2009. The names follow a scheme of association occur very frequently in the Universe, a system of individual with the constellation that the host star pertains to, and names for planets might well rapidly be found equally im- therefore are mostly drawn from Roman-Greek mythology. practicable as it is for stars, as planet discoveries progress.” Other mythologies may also be used given that a suitable 1. This leads to a second argument. It is indeed impractical association is established. to name all stars. But some stars are named nonetheless. In fact, all other classes of astronomical bodies are named.
    [Show full text]
  • Jahresbericht 1997 Zum Titelbild: Ein Neugeborener Stern (Kreuz), Tief in Den Staub Der Molekülwolke L1551 Eingebettet, Aus Der Er Entstand
    Max-Planck-Institut für Astronomie Heidelberg-Königstuhl Jahresbericht 1997 Zum Titelbild: Ein neugeborener Stern (Kreuz), tief in den Staub der Molekülwolke L1551 eingebettet, aus der er entstand. Er ist nicht im Optischen, sondern nur als Infrarotquelle zu erkennen. Er emittiert in Polrichtung einen hellen Jet aus ioni- siertem Gas, beleuchtet einen ausgedehnten Reflexionsnebel, und regt die Herbig-Haro-Objekte HH 28 und HH 29 zum eigenen Leuchten an. Mehr dazu auf Seite 23–29. Max-Planck-Institut für Astronomie Heidelberg-Königstuhl Jahresbericht 1997 Das Max-Planck-Institut für Astronomie Geschäftsführende Direktoren: Prof. Dr. Steven Beckwith (bis 31. 8.), Prof. Dr. Immo Appenzeller (ab 1.8.1998) Wissenschaftliche Mitglieder, Kollegium, Direktoren: Prof. Dr. Immo Appenzeller (ab 1.8.1998, kommissarisch), Prof. Dr. Steven Beckwith, (ab 1. 9. 1998 beurlaubt), Prof. Dr. Hans Elsässer (bis 31. 3. 1997), Prof. Dr. Hans-Walter Rix (ab 1. 1. 1999). Fachbeirat: Prof. R. Bender, München; Prof. R.-J. Dettmar, Bochum; Prof. G. Hasinger, Potsdam; Prof. P. Léna, Meudon; Prof. M. Moles Villlamate, Madrid, Prof. F. Pacini, Firenze; Prof. K.-H. Schmidt, Potsdam; Prof. P.A. Strittmatter, Tuscon; Prof. S.D.M. White, Garching; Prof. L. Woltjer, St. Michel Obs. Derzeit hat das MPIA rund 160 Mitarbeiter, davon 43 Wissenschaftler, 37 Nachwuchs- und Gastwissenschaftler sowie 80 Techniker und Verwaltungsangestellte. Studenten der Fakultät für Physik und Astronomie der Universität Heidelberg führen am Institut Diplom- und Doktorarbeiten aus. In den Werkstätten des Instituts werden ständig Lehrlinge ausgebildet. Anschrift: MPI für Astronomie, Königstuhl 17, D-69117 Heidelberg. Telefon: 0049-6221-5280, Fax: 0049-6221-528246. E-mail: [email protected], Anonymous ftp: ftp.mpia-hd.mpg.de Homepage: http://www.mpia-hd.mpg.de Isophot Datacenter : [email protected].
    [Show full text]
  • Livre-Ovni.Pdf
    UN MONDE BIZARRE Le livre des étranges Objets Volants Non Identifiés Chapitre 1 Paranormal Le paranormal est un terme utilisé pour qualifier un en- mé n'est pas considéré comme paranormal par les semble de phénomènes dont les causes ou mécanismes neuroscientifiques) ; ne sont apparemment pas explicables par des lois scien- tifiques établies. Le préfixe « para » désignant quelque • Les différents moyens de communication avec les chose qui est à côté de la norme, la norme étant ici le morts : naturels (médiumnité, nécromancie) ou ar- consensus scientifique d'une époque. Un phénomène est tificiels (la transcommunication instrumentale telle qualifié de paranormal lorsqu'il ne semble pas pouvoir que les voix électroniques); être expliqué par les lois naturelles connues, laissant ain- si le champ libre à de nouvelles recherches empiriques, à • Les apparitions de l'au-delà (fantômes, revenants, des interprétations, à des suppositions et à l'imaginaire. ectoplasmes, poltergeists, etc.) ; Les initiateurs de la parapsychologie se sont donné comme objectif d'étudier d'une manière scientifique • la cryptozoologie (qui étudie l'existence d'espèce in- ce qu'ils considèrent comme des perceptions extra- connues) : classification assez injuste, car l'objet de sensorielles et de la psychokinèse. Malgré l'existence de la cryptozoologie est moins de cultiver les mythes laboratoires de parapsychologie dans certaines universi- que de chercher s’il y a ou non une espèce animale tés, notamment en Grande-Bretagne, le paranormal est inconnue réelle derrière une légende ; généralement considéré comme un sujet d'étude peu sé- rieux. Il est en revanche parfois associé a des activités • Le phénomène ovni et ses dérivés (cercle de culture).
    [Show full text]
  • Arxiv:2105.11583V2 [Astro-Ph.EP] 2 Jul 2021 Keck-HIRES, APF-Levy, and Lick-Hamilton Spectrographs
    Draft version July 6, 2021 Typeset using LATEX twocolumn style in AASTeX63 The California Legacy Survey I. A Catalog of 178 Planets from Precision Radial Velocity Monitoring of 719 Nearby Stars over Three Decades Lee J. Rosenthal,1 Benjamin J. Fulton,1, 2 Lea A. Hirsch,3 Howard T. Isaacson,4 Andrew W. Howard,1 Cayla M. Dedrick,5, 6 Ilya A. Sherstyuk,1 Sarah C. Blunt,1, 7 Erik A. Petigura,8 Heather A. Knutson,9 Aida Behmard,9, 7 Ashley Chontos,10, 7 Justin R. Crepp,11 Ian J. M. Crossfield,12 Paul A. Dalba,13, 14 Debra A. Fischer,15 Gregory W. Henry,16 Stephen R. Kane,13 Molly Kosiarek,17, 7 Geoffrey W. Marcy,1, 7 Ryan A. Rubenzahl,1, 7 Lauren M. Weiss,10 and Jason T. Wright18, 19, 20 1Cahill Center for Astronomy & Astrophysics, California Institute of Technology, Pasadena, CA 91125, USA 2IPAC-NASA Exoplanet Science Institute, Pasadena, CA 91125, USA 3Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, CA 94305, USA 4Department of Astronomy, University of California Berkeley, Berkeley, CA 94720, USA 5Cahill Center for Astronomy & Astrophysics, California Institute of Technology, Pasadena, CA 91125, USA 6Department of Astronomy & Astrophysics, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802, USA 7NSF Graduate Research Fellow 8Department of Physics & Astronomy, University of California Los Angeles, Los Angeles, CA 90095, USA 9Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA 10Institute for Astronomy, University of Hawai`i,
    [Show full text]
  • A Spectroscopic Study of the Scorpio-Centaurus Association
    PranllQa. Vol. 7, No.3, 1976, pp 160-\ 80. © Prmted in India. A spectroscopic study of the Scorpio-Centaurus association R RAJAMOHAN Indian Institute of Astrophysics, Bangaiore 560034 MS recehcl 5 April 1976 • I' Abstract. Rotational .... elocities as well as hydrogen and he Jlum Ine I'ntensities of .' have been one hundred. and twelve members of the Scorplo-Centaurus aSSOclatlO~ . b h derived. For stars with M~ < 0'0, the distribution of rotational velocitieS of °lt are SJlnlar the upper Scorplus subgroup and the upper Centaurus-Lupus Su b grou P 1 . I and closely resemble those of the field stars. Stars with M, > O' 0, all of w lie 1 are found in th.e dense upper Scorpius region, rotate much faster than their counter­ parts amongst field stars, the Pleiades and Alpha-Persei cluster members. The measured equivalent width of H'Y for 77 stars provide a distance nlOd~\U~ of 6·0±0·09 magnitudes for the association. Evolutionary effects in the del1;~e hydrogen line intensities are found between the two subgroups. The hydrogen- me intensities at all spectral types in the upper Centaurus-Lupus subgroup are systematically smaller than thOse of members in the upper Scorpius subgrouP. Analysis of high dispersion spectra of five members of the association y.ield a helium abundance of Nae(N. = 0·096 ± 0 004. Along with data available In the literature, the mean helium abundance of thirteen stars of this association is found to be 0·098 :±: O· 004 by number. For the two main subgroups of this association, we deflve a value of 0 105 ± 0 001 for the upper Centaurus-Lupus group from three stars and 0·096 ± 0·005 for the upper Scorpius group from ten stars.
    [Show full text]
  • Occurrence and Core-Envelope Structure of 1–4× Earth-Size Planets Around Sun-Like Stars
    Occurrence and core-envelope structure of 1–4× SPECIAL FEATURE Earth-size planets around Sun-like stars Geoffrey W. Marcya,1, Lauren M. Weissa, Erik A. Petiguraa, Howard Isaacsona, Andrew W. Howardb, and Lars A. Buchhavec aDepartment of Astronomy, University of California, Berkeley, CA 94720; bInstitute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822; and cHarvard-Smithsonian Center for Astrophysics, Harvard University, Cambridge, MA 02138 Edited by Adam S. Burrows, Princeton University, Princeton, NJ, and accepted by the Editorial Board April 16, 2014 (received for review January 24, 2014) Small planets, 1–4× the size of Earth, are extremely common planets. The Doppler reflex velocity of an Earth-size planet − around Sun-like stars, and surprisingly so, as they are missing in orbiting at 0.3 AU is only 0.2 m s 1, difficult to detect with an − our solar system. Recent detections have yielded enough informa- observational precision of 1 m s 1. However, such Earth-size tion about this class of exoplanets to begin characterizing their planets show up as a ∼10-sigma dimming of the host star after occurrence rates, orbits, masses, densities, and internal structures. coadding the brightness measurements from each transit. The Kepler mission finds the smallest planets to be most common, The occurrence rate of Earth-size planets is a major goal of as 26% of Sun-like stars have small, 1–2 R⊕ planets with orbital exoplanet science. With three years of Kepler photometry in periods under 100 d, and 11% have 1–2 R⊕ planets that receive 1–4× hand, two groups worked to account for the detection biases in the incident stellar flux that warms our Earth.
    [Show full text]
  • Space Missions for Exoplanet
    Space missions for exoplanet January 3, 2020 Source: The Hindu Manifest pedagogy: As a part of science & technology and geography, questions related to space have been asked both at prelims and mains stage. Finding life in other celestial bodies had always been a human curiosity. Origin of the solar system, exoplanets as prospective resources zone, finding life etc are key objectives of NASA and other space programs. In news: European Space Agency (ESA) has launched CHEOPS exoplanet mission Placing it in syllabus: Exoplanet space missions Static dimensions: What are exoplanets? Current dimensions: Exoplanet missions by NASA Exoplanet missions by ESA and CHEOPS mission Content: What are Exoplanets? The worlds orbiting other stars are called “exoplanets”. They vary in sizes, from gas giants larger than Jupiter to small, rocky planets about as big around as Earth. They can be hot enough to boil metal or locked in deep freeze. They can orbit two suns at once. Some exoplanets are sunless, wandering through the galaxy in permanent darkness. The first exoplanet invented was 51 Pegasi b, a “hot Jupiter” in 1995 which is 50 light-years away that is locked in a four-day orbit around its star. ((The discoverers Didier Queloz and Michel Mayor of 51 Pegasi b shared the 2019 Nobel Prize in Physics for their breakthrough finding)). And a system of three “pulsar planets” had been detected, beginning in 1992. The circumstellar habitable zone (CHZ) also called the Goldilocks zone is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressure.
    [Show full text]
  • The Extragalactic Distance Scale
    The Extragalactic Distance Scale Published in "Stellar astrophysics for the local group" : VIII Canary Islands Winter School of Astrophysics. Edited by A. Aparicio, A. Herrero, and F. Sanchez. Cambridge ; New York : Cambridge University Press, 1998 Calibration of the Extragalactic Distance Scale By BARRY F. MADORE1, WENDY L. FREEDMAN2 1NASA/IPAC Extragalactic Database, Infrared Processing & Analysis Center, California Institute of Technology, Jet Propulsion Laboratory, Pasadena, CA 91125, USA 2Observatories, Carnegie Institution of Washington, 813 Santa Barbara St., Pasadena CA 91101, USA The calibration and use of Cepheids as primary distance indicators is reviewed in the context of the extragalactic distance scale. Comparison is made with the independently calibrated Population II distance scale and found to be consistent at the 10% level. The combined use of ground-based facilities and the Hubble Space Telescope now allow for the application of the Cepheid Period-Luminosity relation out to distances in excess of 20 Mpc. Calibration of secondary distance indicators and the direct determination of distances to galaxies in the field as well as in the Virgo and Fornax clusters allows for multiple paths to the determination of the absolute rate of the expansion of the Universe parameterized by the Hubble constant. At this point in the reduction and analysis of Key Project galaxies H0 = 72km/ sec/Mpc ± 2 (random) ± 12 [systematic]. Table of Contents INTRODUCTION TO THE LECTURES CEPHEIDS BRIEF SUMMARY OF THE OBSERVED PROPERTIES OF CEPHEID
    [Show full text]