Water, Habitability, and Detectability Steve Desch
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Exploring Exoplanet Populations with NASA's Kepler Mission
SPECIAL FEATURE: PERSPECTIVE PERSPECTIVE SPECIAL FEATURE: Exploring exoplanet populations with NASA’s Kepler Mission Natalie M. Batalha1 National Aeronautics and Space Administration Ames Research Center, Moffett Field, 94035 CA Edited by Adam S. Burrows, Princeton University, Princeton, NJ, and accepted by the Editorial Board June 3, 2014 (received for review January 15, 2014) The Kepler Mission is exploring the diversity of planets and planetary systems. Its legacy will be a catalog of discoveries sufficient for computing planet occurrence rates as a function of size, orbital period, star type, and insolation flux.The mission has made significant progress toward achieving that goal. Over 3,500 transiting exoplanets have been identified from the analysis of the first 3 y of data, 100 planets of which are in the habitable zone. The catalog has a high reliability rate (85–90% averaged over the period/radius plane), which is improving as follow-up observations continue. Dynamical (e.g., velocimetry and transit timing) and statistical methods have confirmed and characterized hundreds of planets over a large range of sizes and compositions for both single- and multiple-star systems. Population studies suggest that planets abound in our galaxy and that small planets are particularly frequent. Here, I report on the progress Kepler has made measuring the prevalence of exoplanets orbiting within one astronomical unit of their host stars in support of the National Aeronautics and Space Admin- istration’s long-term goal of finding habitable environments beyond the solar system. planet detection | transit photometry Searching for evidence of life beyond Earth is the Sun would produce an 84-ppm signal Translating Kepler’s discovery catalog into one of the primary goals of science agencies lasting ∼13 h. -
Formation of TRAPPIST-1
EPSC Abstracts Vol. 11, EPSC2017-265, 2017 European Planetary Science Congress 2017 EEuropeaPn PlanetarSy Science CCongress c Author(s) 2017 Formation of TRAPPIST-1 C.W Ormel, B. Liu and D. Schoonenberg University of Amsterdam, The Netherlands ([email protected]) Abstract start to drift by aerodynamical drag. However, this growth+drift occurs in an inside-out fashion, which We present a model for the formation of the recently- does not result in strong particle pileups needed to discovered TRAPPIST-1 planetary system. In our sce- trigger planetesimal formation by, e.g., the streaming nario planets form in the interior regions, by accre- instability [3]. (a) We propose that the H2O iceline (r 0.1 au for TRAPPIST-1) is the place where tion of mm to cm-size particles (pebbles) that drifted ice ≈ the local solids-to-gas ratio can reach 1, either by from the outer disk. This scenario has several ad- ∼ vantages: it connects to the observation that disks are condensation of the vapor [9] or by pileup of ice-free made up of pebbles, it is efficient, it explains why the (silicate) grains [2, 8]. Under these conditions plan- TRAPPIST-1 planets are Earth mass, and it provides etary embryos can form. (b) Due to type I migration, ∼ a rationale for the system’s architecture. embryos cross the iceline and enter the ice-free region. (c) There, silicate pebbles are smaller because of col- lisional fragmentation. Nevertheless, pebble accretion 1. Introduction remains efficient and growth is fast [6]. (d) At approx- TRAPPIST-1 is an M8 main-sequence star located at a imately Earth masses embryos reach their pebble iso- distance of 12 pc. -
Formation of the Solar System (Chapter 8)
Formation of the Solar System (Chapter 8) Based on Chapter 8 • This material will be useful for understanding Chapters 9, 10, 11, 12, 13, and 14 on “Formation of the solar system”, “Planetary geology”, “Planetary atmospheres”, “Jovian planet systems”, “Remnants of ice and rock”, “Extrasolar planets” and “The Sun: Our Star” • Chapters 2, 3, 4, and 7 on “The orbits of the planets”, “Why does Earth go around the Sun?”, “Momentum, energy, and matter”, and “Our planetary system” will be useful for understanding this chapter Goals for Learning • Where did the solar system come from? • How did planetesimals form? • How did planets form? Patterns in the Solar System • Patterns of motion (orbits and rotations) • Two types of planets: Small, rocky inner planets and large, gas outer planets • Many small asteroids and comets whose orbits and compositions are similar • Exceptions to these patterns, such as Earth’s large moon and Uranus’s sideways tilt Help from Other Stars • Use observations of the formation of other stars to improve our theory for the formation of our solar system • Use this theory to make predictions about the formation of other planetary systems Nebular Theory of Solar System Formation • A cloud of gas, the “solar nebula”, collapses inwards under its own weight • Cloud heats up, spins faster, gets flatter (disk) as a central star forms • Gas cools and some materials condense as solid particles that collide, stick together, and grow larger Where does a cloud of gas come from? • Big Bang -> Hydrogen and Helium • First stars use this -
Biosignatures Search in Habitable Planets
galaxies Review Biosignatures Search in Habitable Planets Riccardo Claudi 1,* and Eleonora Alei 1,2 1 INAF-Astronomical Observatory of Padova, Vicolo Osservatorio, 5, 35122 Padova, Italy 2 Physics and Astronomy Department, Padova University, 35131 Padova, Italy * Correspondence: [email protected] Received: 2 August 2019; Accepted: 25 September 2019; Published: 29 September 2019 Abstract: The search for life has had a new enthusiastic restart in the last two decades thanks to the large number of new worlds discovered. The about 4100 exoplanets found so far, show a large diversity of planets, from hot giants to rocky planets orbiting small and cold stars. Most of them are very different from those of the Solar System and one of the striking case is that of the super-Earths, rocky planets with masses ranging between 1 and 10 M⊕ with dimensions up to twice those of Earth. In the right environment, these planets could be the cradle of alien life that could modify the chemical composition of their atmospheres. So, the search for life signatures requires as the first step the knowledge of planet atmospheres, the main objective of future exoplanetary space explorations. Indeed, the quest for the determination of the chemical composition of those planetary atmospheres rises also more general interest than that given by the mere directory of the atmospheric compounds. It opens out to the more general speculation on what such detection might tell us about the presence of life on those planets. As, for now, we have only one example of life in the universe, we are bound to study terrestrial organisms to assess possibilities of life on other planets and guide our search for possible extinct or extant life on other planetary bodies. -
University of Groningen Evaluating Galactic Habitability Using High
University of Groningen Evaluating galactic habitability using high-resolution cosmological simulations of galaxy formation Forgan, Duncan; Dayal, Pratika; Cockell, Charles; Libeskind, Noam Published in: International Journal of Astrobiology DOI: 10.1017/S1473550415000518 IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Please check the document version below. Document Version Final author's version (accepted by publisher, after peer review) Publication date: 2017 Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Forgan, D., Dayal, P., Cockell, C., & Libeskind, N. (2017). Evaluating galactic habitability using high- resolution cosmological simulations of galaxy formation. International Journal of Astrobiology, 16(1), 60–73. https://doi.org/10.1017/S1473550415000518 Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons). The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license. More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne- amendment. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. -
Monday, November 13, 2017 WHAT DOES IT MEAN to BE HABITABLE? 8:15 A.M. MHRGC Salons ABCD 8:15 A.M. Jang-Condell H. * Welcome C
Monday, November 13, 2017 WHAT DOES IT MEAN TO BE HABITABLE? 8:15 a.m. MHRGC Salons ABCD 8:15 a.m. Jang-Condell H. * Welcome Chair: Stephen Kane 8:30 a.m. Forget F. * Turbet M. Selsis F. Leconte J. Definition and Characterization of the Habitable Zone [#4057] We review the concept of habitable zone (HZ), why it is useful, and how to characterize it. The HZ could be nicknamed the “Hunting Zone” because its primary objective is now to help astronomers plan observations. This has interesting consequences. 9:00 a.m. Rushby A. J. Johnson M. Mills B. J. W. Watson A. J. Claire M. W. Long Term Planetary Habitability and the Carbonate-Silicate Cycle [#4026] We develop a coupled carbonate-silicate and stellar evolution model to investigate the effect of planet size on the operation of the long-term carbon cycle, and determine that larger planets are generally warmer for a given incident flux. 9:20 a.m. Dong C. F. * Huang Z. G. Jin M. Lingam M. Ma Y. J. Toth G. van der Holst B. Airapetian V. Cohen O. Gombosi T. Are “Habitable” Exoplanets Really Habitable? A Perspective from Atmospheric Loss [#4021] We will discuss the impact of exoplanetary space weather on the climate and habitability, which offers fresh insights concerning the habitability of exoplanets, especially those orbiting M-dwarfs, such as Proxima b and the TRAPPIST-1 system. 9:40 a.m. Fisher T. M. * Walker S. I. Desch S. J. Hartnett H. E. Glaser S. Limitations of Primary Productivity on “Aqua Planets:” Implications for Detectability [#4109] While ocean-covered planets have been considered a strong candidate for the search for life, the lack of surface weathering may lead to phosphorus scarcity and low primary productivity, making aqua planet biospheres difficult to detect. -
IS HABITABILITY CONSTRAINED by PHYSICS OR BIOLOGY? the CASE for a GAIAN BOTTLENECK. Charles. H. Lineweaver1 and Aditya Chopra1
Astrobiology Science Conference 2015 (2015) 7276.pdf IS HABITABILITY CONSTRAINED BY PHYSICS OR BIOLOGY? THE CASE FOR A GAIAN BOTTLENECK. Charles. H. Lineweaver1 and Aditya Chopra1, 1Planetary Science Institute, Research School of Astronomy and Astrophysics and Research School of Earth Sciences, Australian National University, Australia, [email protected], [email protected] The prerequisites and ingredients for life seem to Earth. We are proposing a sequence of events that can be abundantly available in the universe. However, the be summarized as: (1) uninhabitably hot, high universe does not seem to be teeming with life. The bombardment rate during planetary accretion (2) most common explanation for this is a low probability cooler, reduced bombardment (3) emergence of life in for the emergence of life (an emergence bottleneck), planetary environments that tend to evolve away from notionally due to the intricacies of the molecular habitability, continuous volatile loss. Then either (4a) recipe. Here we present an alternative explanation: a the inability of life to control atmospheric volatiles and Gaian bottleneck [1]. If life emerges on a planet, it maintain habitabililty, thus leading to extinction (left only rarely evolves quickly enough to regulate panel in figure) or (4b) the rapid evolution of Gaian temperature through albedo and atmospheric volatiles regulation and the maintenance of habitability (right and maintain habitability. Such a Gaian bottleneck panel in figure) suggests that (i) extinction is the cosmic default for most life that has ever emerged on the surface of wet Gaian Regulation rocky planets in the universe and (ii) rocky planets +2 Gyr +2 Gyr need to be inhabited, to remain habitable. -
Why Should We Care About TRAPPIST-1?
PUBLISHED: 27 MARCH 2017 | VOLUME: 1 | ARTICLE NUMBER: 0104 news & views EXOPLANETS Why should we care about TRAPPIST-1? The discovery of a system of six (possibly system we’ve found with terrestrial planets seven) terrestrial planets around the tightly packed together and in resonance. TRAPPIST-1 star, announced in a paper Their orbits are also all co-planar, as the by Michaël Gillon and collaborators image shows, and luckily for us this orbital (Nature 542, 456–460; 2017) attracted a plane passes through the line of sight great deal of attention from researchers between us and TRAPPIST-1: all these as well as the general public. Reactions planets are ‘transiting’. This is much more ranged from the enthusiastic — already than a simple technical detail, as it allows us hypothesizing a string of inhabited to characterize all their atmospheres — an planets — to those who felt that it essential step to understand their climate didn’t add anything substantial to our and propensity for habitability. current knowledge of exoplanets and Finally and maybe most importantly, was ultimately not worth the hype. The these planets are distributed over all of cover of the Nature issue hosting the the three zones related to different phases paper (pictured), made by Robert Hurt, (IPAC) HURT NASA/JPL-CALTECH/ROBERT of water, as cleverly represented by the a visualization scientist at Caltech, is a illustration. However, this information, fine piece of artwork, but it also helps us They can thus be called ‘terrestrial’ without linked to the concept of habitable or in assessing the actual relevance of the any qualms about terminology. -
Comparative Habitability of Transiting Exoplanets
Draft version October 1, 2015 A Preprint typeset using LTEX style emulateapj v. 04/17/13 COMPARATIVE HABITABILITY OF TRANSITING EXOPLANETS Rory Barnes1,2,3, Victoria S. Meadows1,2, Nicole Evans1,2 Draft version October 1, 2015 ABSTRACT Exoplanet habitability is traditionally assessed by comparing a planet’s semi-major axis to the location of its host star’s “habitable zone,” the shell around a star for which Earth-like planets can possess liquid surface water. The Kepler space telescope has discovered numerous planet candidates near the habitable zone, and many more are expected from missions such as K2, TESS and PLATO. These candidates often require significant follow-up observations for validation, so prioritizing planets for habitability from transit data has become an important aspect of the search for life in the universe. We propose a method to compare transiting planets for their potential to support life based on transit data, stellar properties and previously reported limits on planetary emitted flux. For a planet in radiative equilibrium, the emitted flux increases with eccentricity, but decreases with albedo. As these parameters are often unconstrained, there is an “eccentricity-albedo degeneracy” for the habitability of transiting exoplanets. Our method mitigates this degeneracy, includes a penalty for large-radius planets, uses terrestrial mass-radius relationships, and, when available, constraints on eccentricity to compute a number we call the “habitability index for transiting exoplanets” that represents the relative probability that an exoplanet could support liquid surface water. We calculate it for Kepler Objects of Interest and find that planets that receive between 60–90% of the Earth’s incident radiation, assuming circular orbits, are most likely to be habitable. -
The Planetary Luminosity Problem:" Missing Planets" and The
Draft version March 27, 2020 Typeset using LATEX twocolumn style in AASTeX62 The Planetary Luminosity Problem: \Missing Planets" and the Observational Consequences of Episodic Accretion Sean D. Brittain,1, ∗ Joan R. Najita,2 Ruobing Dong,3 and Zhaohuan Zhu4 1Clemson University 118 Kinard Laboratory Clemson, SC 29634, USA 2National Optical Astronomical Observatory 950 North Cherry Avenue Tucson, AZ 85719, USA 3Department of Physics & Astronomy University of Victoria Victoria BC V8P 1A1, Canada 4Department of Physics and Astronomy University of Nevada, Las Vegas 4505 S. Maryland Pkwy. Las Vegas, NV 89154, USA (Received March 27, 2020; Revised TBD; Accepted TBD) Submitted to ApJ ABSTRACT The high occurrence rates of spiral arms and large central clearings in protoplanetary disks, if interpreted as signposts of giant planets, indicate that gas giants form commonly as companions to young stars (< few Myr) at orbital separations of 10{300 au. However, attempts to directly image this giant planet population as companions to more mature stars (> 10 Myr) have yielded few successes. This discrepancy could be explained if most giant planets form \cold start," i.e., by radiating away much of their formation energy as they assemble their mass, rendering them faint enough to elude detection at later times. In that case, giant planets should be bright at early times, during their accretion phase, and yet forming planets are detected only rarely through direct imaging techniques. Here we explore the possibility that the low detection rate of accreting planets is the result of episodic accretion through a circumplanetary disk. We also explore the possibility that the companion orbiting the Herbig Ae star HD 142527 may be a giant planet undergoing such an accretion outburst. -
PLANETARY CANDIDATES OBSERVED by Kepler. VIII. a FULLY AUTOMATED CATALOG with MEASURED COMPLETENESS and RELIABILITY BASED on DATA RELEASE 25
Draft version October 13, 2017 Typeset using LATEX twocolumn style in AASTeX61 PLANETARY CANDIDATES OBSERVED BY Kepler. VIII. A FULLY AUTOMATED CATALOG WITH MEASURED COMPLETENESS AND RELIABILITY BASED ON DATA RELEASE 25 Susan E. Thompson,1, 2, 3, ∗ Jeffrey L. Coughlin,2, 1 Kelsey Hoffman,1 Fergal Mullally,1, 2, 4 Jessie L. Christiansen,5 Christopher J. Burke,2, 1, 6 Steve Bryson,2 Natalie Batalha,2 Michael R. Haas,2, y Joseph Catanzarite,1, 2 Jason F. Rowe,7 Geert Barentsen,8 Douglas A. Caldwell,1, 2 Bruce D. Clarke,1, 2 Jon M. Jenkins,2 Jie Li,1 David W. Latham,9 Jack J. Lissauer,2 Savita Mathur,10 Robert L. Morris,1, 2 Shawn E. Seader,11 Jeffrey C. Smith,1, 2 Todd C. Klaus,2 Joseph D. Twicken,1, 2 Jeffrey E. Van Cleve,1 Bill Wohler,1, 2 Rachel Akeson,5 David R. Ciardi,5 William D. Cochran,12 Christopher E. Henze,2 Steve B. Howell,2 Daniel Huber,13, 14, 1, 15 Andrej Prša,16 Solange V. Ramírez,5 Timothy D. Morton,17 Thomas Barclay,18 Jennifer R. Campbell,2, 19 William J. Chaplin,20, 15 David Charbonneau,9 Jørgen Christensen-Dalsgaard,15 Jessie L. Dotson,2 Laurance Doyle,21, 1 Edward W. Dunham,22 Andrea K. Dupree,9 Eric B. Ford,23, 24, 25, 26 John C. Geary,9 Forrest R. Girouard,27, 2 Howard Isaacson,28 Hans Kjeldsen,15 Elisa V. Quintana,18 Darin Ragozzine,29 Avi Shporer,30 Victor Silva Aguirre,15 Jason H. Steffen,31 Martin Still,8 Peter Tenenbaum,1, 2 William F. -
Strong Accretion on a Deuterium-Burning Brown Dwarf? F
Astronomy & Astrophysics manuscript no. GY11* c ESO 2010 June 27, 2010 Strong accretion on a deuterium-burning brown dwarf? F. Comeron´ 1, L. Testi1, and A. Natta2 1 ESO, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei Munchen,¨ Germany e-mail: [email protected] 2 Osservatorio Astrofisico di Arcetri, INAF, Largo E. Fermi 5, I-50125 Firenze, Italy Received ; accepted ABSTRACT Context. The accretion processes that accompany the earliest stages of star formation have been shown in recent years to extend to masses well below the substellar limit, and even to masses close to the deuterium-burning limit, suggesting that the features characteristic of the T Tauri phase are also common to brown dwarfs. Aims. We discuss new observations of GY 11, a young brown dwarf in the ρ Ophiuchi embedded cluster. Methods. We have obtained for the first time low resolution long-slit spectroscopy of GY 11 in the red visible region, using the FORS1 instrument at the VLT. The spectral region includes accretion diagnostic lines such as Hα and the CaII infrared triplet. Results. The visible spectrum allows us to confirm that GY 11 lies well below the hydrogen-burning limit, in agreement with earlier findings based on the near-infrared spectral energy distribution. We obtain an improved derivation of its physical parameters, which −3 suggest that GY 11 is on or near the deuterium-burning phase. We estimate a mass of 30 MJup, a luminosity of 6 × 10 M , and a temperature of 2700 K. We detect strong Hα and CaII triplet emission, and we estimate from the latter an accretion rate M˙ acc = −10 −1 9:5 × 10 M yr , which places GY 11 among the objects with the largest M˙ acc=M∗ ratios measured thus far in their mass range.