Protostars and Planets VI

Protostars and Planets VI

Henrik Beuther
Ralf S. Klessen
Cornelis P. Dullemond
Thomas Henning
With the assistance of Renée Dotson
https://www.jstor.org/stable/j.ctt183gxt8
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  • Book Info
    Protostars and Planets VI
    Book Description:

    The revolutionary discovery of thousands of confirmed and candidate planets beyond the solar system brings forth the most fundamentalquestion: How do planets and their host stars form and evolve? Protostars and Planets VI brings together more than 250 contributing authors at the forefront of their field, conveying the latest results in this research area and establishing a new foundation for advancing our understanding of stellar and planetary formation.Continuing the tradition of the Protostars and Planets series, this latest volume uniquely integrates the cross-disciplinary aspects of this broad field. Covering an extremely wide range of scales, from the formation of large clouds in our Milky Way galaxy down to small chondrules in our solar system, Protostars and Planets VI takes an encompassing view with the goal of not only highlighting what we know but, most importantly, emphasizing the frontiers of what we do not know.As a vehicle for propelling forward new discoveries on stars, planets, and their origins, this latest volume in the Space Science Series is an indispensable resource for both current scientists and new students in astronomy, astrophysics, planetary science, and the study of meteorites.

    eISBN: 978-0-8165-9876-2
    Subjects: General Science

Table of Contents

  1. Front Matter
    (pp. i-viii)
  2. Table of Contents
    (pp. ix-xii)
  3. Scientific Advisory Committee and List of Collaborating Authors
    (pp. xiii-xiv)
  4. Preface
    (pp. xv-xvi)
    Henrik Beuther, Ralf Klessen, Cornelis Dullemond and Thomas Henning
  5. PART I: MOLECULAR CLOUDS AND STAR FORMATION
    • Formation of Molecular Clouds and Global Conditions for Star Formation
      (pp. 3-26)
      Clare L. Dobbs, Mark R. Krumholz, Javier Ballesteros-Paredes, Alberto D. Bolatto, Yasuo Fukui, Mark Heyer, Mordecai-Mark Mac Low, Eve C. Ostriker and Enrique Vázquez-Semadeni

      Stars form in a cold, dense, molecular phase of the interstellar medium (ISM) that appears to be organized into coherent, localized volumes or clouds. The star formation history of the universe, the evolution of galaxies, and the formation of planets in stellar environments are all coupled to the formation of these clouds, the collapse of unstable regions within them to stars, and the clouds’ final dissipation. The physics of these regions is complex, and descriptions of cloud structure and evolution remain incomplete and require continued exploration. Here we review the current status of observations and theory of molecular clouds, focusing...

    • From Filamentary Networks to Dense Cores in Molecular Clouds: Toward a New Paradigm for Star Formation
      (pp. 27-52)
      Philippe André, James Di Francesco, Derek Ward-Thompson, Shu-ichiro Inutsuka, Ralph E. Pudritz and Jaime Pineda

      The physics controlling the earliest phases of star formation is not yet well understood. Improving our global understanding of these phases is crucial for gaining insight into the general inefficiency of the star-formation process, the global rate of star formation on galactic scales, the origin of stellar masses, and the birth of planetary systems.

      SinceProtostars and Planets V(Reipurth et al., 2007) seven years ago, one area that has seen the most dramatic advances has been the characterization of the link between star formation and the structure of the cold interstellar medium (ISM). In particular, extensive studies of the...

    • The Origin and Universality of the Stellar Initial Mass Function
      (pp. 53-76)
      Stella S. R. Offner, Paul C. Clark, Patrick Hennebelle, Nathan Bastian, Matthew R. Bate, Philip F. Hopkins, Estelle Moraux and Anthony P. Whitworth

      Measuring the stellar initial mass function (IMF), and understanding its genesis, is a central issue in the study of star formation. It also has a fundamental bearing on many other areas of astronomy, e.g., modeling the microphysics of galactic structure and evolution, and tracking the buildup of the heavy elements that are essential for planet formation and for life. Since it appears that the formation and architecture of a planetary system strongly depends on the mass of the host star, and — for stars in clusters — on feedback effects from nearby massive stars, an understanding of the IMF is...

    • The Star Formation Rate of Molecular Clouds
      (pp. 77-100)
      Paolo Padoan, Christoph Federrath, Gilles Chabrier, Neal J. Evans II, Doug Johnstone, Jes K. Jørgensen, Christopher F. McKee and Åke Nordlund

      Understanding and modeling the star formation rate (SFR) is a central goal of a theory of star formation. Cosmological simulations of galaxy formation demonstrate the impact of SFR models on galaxy evolution (Agertz et al., 2013), but they neither include star formation self-consistently, nor its feedback mechanisms. They must rely instead on suitable subgrid-scale models to include the effects of star formation and feedback.

      The SFR has been a fundamental problem in astrophysics since the 1970s, when it was shown that the gas depletion time in our Galaxy is much longer than any characteristic free-fall time of star-forming gas (Zuckerman...

    • The Link Between Magnetic Fields and Cloud/Star Formation
      (pp. 101-124)
      Hua-bai Li, Alyssa Goodman, T. K. Sridharan, Martin Houde, Zhi-Yun Li, Giles Novak and Kwok Sun Tang

      How molecular clouds form and then fragment into filaments, cores, protostellar disks, and finally stars is still mysterious. The existence of large-scale magnetic fields (B fields) in the interstellar medium (ISM) was first shown byHiltner(1951) andHall(1951) nearly 65 years ago. On the cloud-formation scale (103–102pc), B-field strength is expected to determine whether a cloud can rotate with the angular momentum inherited from galactic shear and/or turbulence. The fragmentation of a cloud (e.g., the formation of filamentary structures; see the chapter by André et al. in this volume) also strongly depends on the cloud B-field...

    • The Milky Way as a Star Formation Engine
      (pp. 125-148)
      Sergio Molinari, John Bally, Simon Glover, Toby Moore, Alberto Noriega-Crespo, René Plume, Leonardo Testi, Enrique Vázquez-Semadeni, Annie Zavagno, Jean-Philippe Bernard and Peter Martin

      Phase changes in the Galactic interstellar medium (ISM) are to a large extent controlled by the formation of massive stars. The cycling of the ISM from mostly neutral atomic (Hi) clouds into molecular (H2) clouds, traced by low-excitation species such as OH and CO, leads to the formation of dense, self-gravitating clumps and cores traced by high-density species such as NH3, CS, HCN, HCO+, and N2H+, and by other even higher dipole-moment molecules in regions where stars form.

      Dust continuum emission in the mid-infrared (IR), far-IR, submillimeter, and millimeter ranges of the spectrum reveal progressively cooler and higher column density...

    • Massive Star Formation
      (pp. 149-172)
      Jonathan C. Tan, Maria T. Beltrán, Paola Caselli, Francesco Fontani, Asunción Fuente, Mark R. Krumholz, Christopher F. McKee and Andrea Stolte

      Across the universe, massive stars play dominant roles in terms of their feedback and their synthesis and dispersal of heavy elements. Achieving a full theoretical understanding of massive star formation is thus an important goal of contemporary astrophysics. This effort can also be viewed as a major component of the development of a general theory of star formation that seeks to explain the birth of stars of all masses and from all varieties of star-forming environments.

      Two main classes of theory are under active study: core accretion and competitive accretion. In core accretion, extending “standard” low-mass star formation theory (Shu...

    • The Earliest Stages of Star and Planet Formation: Core Collapse, and the Formation of Disks and Outflows
      (pp. 173-194)
      Zhi-Yun Li, Robi Banerjee, Ralph E. Pudritz, Jes K. Jørgensen, Hsien Shang, Ruben Krasnopolsky and Anaëlle Maury

      This review focuses on the earliest stages of star and planet formation, with an emphasis on the origins of early disks and outflows, and conditions that characterize the earliest stages of planet formation.

      The importance of disks is obvious. They are the birthplace of planets, including those in our solar system. Nearly 1000 exoplanets have been discovered to date (http://exoplanet.eu) (see the chapters by Chabrier et al. and Helled et al. in this volume). The prevalence of planets indicates that disks must be common at least at some point in time around Sun-like stars. Observations show that this is indeed...

    • The Evolution of Protostars: Insights from Ten Years of Infrared Surveys with Spitzer and Herschel
      (pp. 195-218)
      Michael M. Dunham, Amelia M. Stutz, Lori E. Allen, Neal J. Evans II, William J. Fischer, S. Thomas Megeath, Philip C. Myers, Stella S. R. Offner, Charles A. Poteet, John J. Tobin and Eduard I. Vorobyov

      The formation of stars occurs in dense cores of molecular clouds, where gravity finally overwhelms turbulence, magnetic fields, and thermal pressure. This review assesses the current understanding of the early stages of this process, focusing on the evolutionary progression from dense cores up to the stage of a star and disk without a surrounding envelope: the protostellar phase of evolution.

      Because of the obscuration at short wavelengths by dust and the consequent reemission at longer wavelengths, protostars are best studied at infrared and radio wavelengths, using both continuum emission from dust and spectral lines. At the time of the last...

    • Ages of Young Stars
      (pp. 219-242)
      David R. Soderblom, Lynne A. Hillenbrand, Rob D. Jeffries, Eric E. Mamajek and Tim Naylor

      We know the timing of key events in the early history of our solar system from meteorites because we can apply radiometric dating techniques to samples in a laboratory. From this we infer the Sun’s age, a very precise one, but even the Sun itself does not directly reveal its age in its visible properties. The techniques for age-dating stars, and thereby other planetary systems, are of much lower precision. Establishing accurate or even precise ages for stars remains difficult, especially for young stars at the very stages where many interesting things, including planet formation and subsequent dynamical evolution, are...

    • Star Cluster Formation and Feedback
      (pp. 243-266)
      Mark R. Krumholz, Matthew R. Bate, Héctor G. Arce, James E. Dale, Robert Gutermuth, Richard I. Klein, Zhi-Yun Li, Fumitaka Nakamura and Qizhou Zhang

      Newborn stars have profound effects on their birth environments, and any complete theory for star formation must include them. Perhaps the best argument for this statement is an image such as Fig. 1, which shows 30 Doradus, the largest Hii region in the Local Group, powered by the cluster NGC 2070 and its 2400 OB stars (Parker, 1993). The figure illustrates several of the routes by which young stars can influence their surroundings. Observations reveal extensive 8-μm emission around the outer rim of the structure shown radiation from young stars. On the inner rim of the cavity-like structures, Hα emission...

    • Multiplicity in Early Stellar Evolution
      (pp. 267-290)
      Bo Reipurth, Cathie J. Clarke, Alan P. Boss, Simon P. Goodwin, Luis Felipe Rodríguez, Keivan G. Stassun, Andrei Tokovinin and Hans Zinnecker

      Many reviews have been written on pre-main-sequence binaries over the past 25 years, e.g.,Reipurth(1988),Zinnecker(1989),Mathieu(1994), andGoodwin(2010), and particular mention should be made of IAU Symposium No. 200 (Zinnecker and Mathieu, 2001), which is still today a useful reference. Most recently,Duchêne and Kraus(2013) review the binarity for stars of all masses and ages.

      Stimulated by the growing discoveries of multiple systems among young stars, there is increasing interest in the idea, first formulated byLarson(1972), that all stars may be born in small multiple systems, and that the mixture of single,...

    • The Formation and Early Evolution of Young Massive Clusters
      (pp. 291-314)
      Steven N. Longmore, J. M. Diederik Kruijssen, Nate Bastian, John Bally, Jill Rathborne, Leonardo Testi, Andrea Stolte, James Dale, Eli Bressert and Joao Alves

      As exemplified by the chapters in this volume, the basic theoretical framework describing the formation of isolated, low-mass stars is now well established. This framework is underpinned by detailed observational studies of the closest star-forming regions. But how typical is the star and planet formation in Taurus, Perseus, or even Orion compared to the formation environment of most stars across cosmological timescales?

      The fact that half the star formation in the Galaxy is currently taking place in the 24 most massive giant molecular clouds (GMCs) (Lee et al., 2012) suggests that even in the Milky Way at the present day,...

  6. PART II: DISK FORMATION AND EVOLUTION
    • Physical and Chemical Structure of Planet-Forming Disks Probed by Millimeter Observations and Modeling
      (pp. 317-338)
      Anne Dutrey, Dmitry Semenov, Edwige Chapillon, Uma Gorti, Stéphane Guilloteau, Franck Hersant, Michiel Hogerheijde, Meredith Hughes, Gwendolyn Meeus, Hideko Nomura, Vincent Piétu, Chunhua Qi and Valentine Wakelam

      The evolution of the gas and dust in protoplanetary disks is a key element that regulates the efficiency, diversity, and timescale of planet formation. The situation is complicated by the fact that the dust and gas physically and chemically interact atop the disk structure, which evolves with time. Initially, small dust grains are dynamically well-coupled to the gas and are later assembled by grain growth in bigger centimeter-sized particles that settle toward the disk mid-plane (see the chapter by Testi et al. in this volume). After large grains become dynamically decoupled from the gas, they become subject to head wind...

    • Dust Evolution in Protoplanetary Disks
      (pp. 339-362)
      Leonardo Testi, Tilman Birnstiel, Luca Ricci, Sean Andrews, Jürgen Blum, John Carpenter, Carsten Dominik, Andrea Isella, Antonella Natta, Jonathan P. Williams and David J. Wilner

      In this chapter we will discuss the evolution of dust in protoplanetary disks, focusing on the processes of grain growth and the observational consequences of this process. In the standard scenario for planet formation, this is the phase in which the solids grow from micrometer-sized particles, which are present in the molecular cloud cores out of which stars and protoplanetary disks are formed, to centimeter-sized and beyond on the path to become planetesimals. This is the last stage of solid growth that is directly observable before the formation of large, planetary-sized bodies that can be individually observed. As this phase...

    • Volatiles in Protoplanetary Disks
      (pp. 363-386)
      Klaus M. Pontoppidan, Colette Salyk, Edwin A. Bergin, Sean Brittain, Bernard Marty, Olivier Mousis and Karin I. Öberg

      The study of the role of ices and volatile compounds in the formation and evolution of planetary systems has a long and venerable history. Up until the late twentieth century, due to the lack of knowledge of exoplanetary systems, the solar system was the only case study. Consequently, some of the earliest pieces of firm evidence for abundant ices in planetary systems came from cometary spectroscopy, showing the photodissociation products of what could only be common ices, such as water and ammonia (Whipple, 1950). Following early suggestions by, e.g.,Kuiper(1953), the presence of water ice in the rings of...

    • Episodic Accretion in Young Stars
      (pp. 387-410)
      Marc Audard, Péter Ábrahám, Michael M. Dunham, Joel D. Green, Nicolas Grosso, Kenji Hamaguchi, Joel H. Kastner, Ágnes Kόspál, Giuseppe Lodato, Marina M. Romanova, Stephen L. Skinner, Eduard I. Vorobyov and Zhaohuan Zhu

      Episodic accretion has become a recent focus of attention in the star- and planet-formation community, turning into a central topic to understand the evolution of protostars and accreting young stars. Initially identified as young stellar objects (YSOs) with strong, long-lived optical outbursts (Herbig, 1966, 1977), FU Orionis objects (hereafter FUors) have triggered many investigations to understand the eruptive phenomenon. Several reviews have been published (Herbig, 1977;Reipurth, 1990;Hartmann et al., 1993;Hartmann, 1991;Kenyon, 1995a,b;Bell et al., 2000;Hartmann and Kenyon, 1996) [see also the specific chapter on the FU Ori phenomenon inHartmann(2008) and the recent...

    • Transport and Accretion in Planet-Forming Disks
      (pp. 411-432)
      Neal J. Turner, Sébastien Fromang, Charles Gammie, Hubert Klahr, Geoffroy Lesur, Mark Wardle and Xue-Ning Bai

      A key to the evolution of the planet-forming material in protostellar disks is the angular momentum. The angular momentum per unit mass of gas orbiting just above the star’s surface is only 1% that of gas near the disk’s outer edge. Sustaining the accretion on the star therefore requires taking almost all the angular momentum out of the accreting matter. Since the angular momentum cannot be destroyed, it must be handed off to other material. The gas receiving the angular momentum could move radially outward, or could join outflows escaping above and below the disk. The gas losing angular momentum...

    • [Illustrations]
      (pp. None)
    • Angular Momentum Evolution of Young Low-Mass Stars and Brown Dwarfs: Observations and Theory
      (pp. 433-450)
      Jérôme Bouvier, Sean P. Matt, Subhanjoy Mohanty, Aleks Scholz, Keivan G. Stassun and Claudio Zanni

      The angular momentum content of a newly born star is one of the fundamental quantities, like mass and metallicity, that durably impacts the star’s properties and evolution. Rotation influences the star’s internal structure, energy transport, and the mixing processes in the stellar interior, which are reflected in surface elemental abundances. It is also the main driver for magnetic activity, from X-ray luminosity to ultraviolet (UV) flux and surface spots, which are the ultimate source of stellar winds. Studying the initial angular momentum content of stars and its evolution throughout the star’s lifetime brings unique clues to the star-formation process, to...

    • Jets and Outflows from Star to Cloud: Observations Confront Theory
      (pp. 451-474)
      A. Frank, T. P. Ray, S. Cabrit, P. Hartigan, H. G. Arce, F. Bacciotti, J. Bally, M. Benisty, J. Eislöffel, M. Güdel, S. Lebedev, B. Nisini and A. Raga

      In many ways the discovery that star formation involvesoutflowas well asinflowfrom gravitational collapse marked the beginning of modern studies of the assembly of stars. Jets and outflows were the first and most easily observed recognition that the narrative of star formation would include many players and processes beyond the spherical collapse of clouds. The extraordinary progress made in the study of protostellar jets and outflows since the first discovery of Herbig-Haro (HH) objects (1950s), HH jets (1980s), and molecular outflows (1980s) also reflects the growing power and sophistication of star-formation science. The combination of ever-higher-resolution observational...

    • The Dispersal of Protoplanetary Disks
      (pp. 475-496)
      Richard Alexander, Ilaria Pascucci, Sean Andrews, Philip Armitage and Lucas Cieza

      The evolution and eventual dispersal of protoplanetary disks play crucial roles in planet formation. Protoplanetary disks are a natural consequence of star formation, spun up by angular momentum conservation during gravitational collapse. The simple fact that these disks are observed to accrete tells us that they evolve, and observations of diskless stars show that final gas disk dispersal is very efficient. Disk dispersal therefore sets a strict limit on the timescale for gas-giant planet formation. Removal of disk gas can also alter the disk’s chemical composition, which has important implications for planet formation, and as disk clearing halts planet migration...

    • An Observational Perspective of Transitional Disks
      (pp. 497-520)
      Catherine Espaillat, James Muzerolle, Joan Najita, Sean Andrews, Zhaohuan Zhu, Nuria Calvet, Stefan Kraus, Jun Hashimoto, Adam Kraus and Paola D’Alessio

      Disks around young stars are thought to be the sites of planet formation. However, many questions exist concerning how the gas and dust in the disk evolve into a planetary system. Observations of T Tauri stars (TTS) may provide insights into these questions, and a subset of TTS, the “transitional disks,” have gained increasing attention in this regard. The unusual spectral energy distributions (SEDs) of transitional disks (which feature infrared excess deficits) may indicate that they have developed significant radial structure.

      Transitional disk SEDs were first identified byStrom et al. (1989) andSkrutskie et al. (1990) from near-infrared (NIR)...

    • Observations, Modeling, and Theory of Debris Disks
      (pp. 521-544)
      Brenda C. Matthews, Alexander V. Krivov, Mark C. Wyatt, Geoffrey Bryden and Carlos Eiroa

      Our evolving understanding of debris disks through the Protostars and Planets (PP) series was succintly summarized byMeyer et al. (2007), emphasizing the important role they play in studies of planetary systems and stressing the need to resolve disks to break the degeneracies inherent in spectral energy distribution (SED) modeling, setting well the stage for the near-decade of debris disk science that has come and gone since. The Spitzer Space Telescope’s debris disk surveys are complete and now in the literature, and these are augmented significantly by those of the Herschel Space Observatory, which will have a lasting legacy owing...

  7. PART III: PLANETARY SYSTEMS — SEARCH, FORMATION, AND EVOLUTION
    • The Multifaceted Planetesimal Formation Process
      (pp. 547-570)
      Anders Johansen, Jürgen Blum, Hidekazu Tanaka, Chris Ormel, Martin Bizzarro and Hans Rickman

      Most stars are born surrounded by a thin protoplanetary disk with a characteristic mass between 0.01% and 10% of the mass of the central star (Andrews and Williams, 2005). Planetesimal formation takes place as the embedded dust and ice particles collide and grow to ever larger bodies. Tiny particles collide gently due to Brownian motion, while larger aggregates achieve higher and higher collision speeds as they gradually decouple from the smallest eddies of the turbulent gas and thus no longer inherit the incompressibility of the gas flow (Voelk et al., 1980). The gas disk is partially pressure-supported in the radial...

    • Early Thermal Evolution of Planetesimals and Its Impact on Processing and Dating of Meteoritic Material
      (pp. 571-594)
      Hans-Peter Gail, Mario Trieloff, Doris Breuer and Tilman Spohn

      Radioisotopic ages for meteorites and their components provide constraints on the evolution of small bodies: timescales of accretion, thermal and aqueous metamorphism, differentiation, cooling, and impact metamorphism. There have been many debates about the nature of the heating source of small bodies, realizing that the decay heat of long-lived nuclides (e.g.,40K, U, and Th) is insufficient. Most studies prefer the decay heat of26Al as a main heat source driving differentiation and metamorphism, and possibly60Fe, although recent studies (Tang and Dauphas, 2012;Telus et al., 2012) indicate that its abundance is probably too low to induce major effects....

    • Terrestrial Planet Formation at Home and Abroad
      (pp. 595-618)
      Sean N. Raymond, Eiichiro Kokubo, Alessandro Morbidelli, Ryuji Morishima and Kevin J. Walsh

      The term “terrestrial planet” evokes landscapes of a rocky planet like Earth or Mars but given recent discoveries it has become somewhat ambiguous. Does a 5-Msuper-Earth count as a terrestrial planet? What about the Mars-sized moon of a giant planet? These objects are terrestrial planetsized, but their compositions and corresponding landscapes probably differ significantly from those of our terrestrial planets. In addition, while Earth is thought to have formed via successive collisions of planetesimals and planetary embryos, the other objects may have formed via different mechanisms. For instance, under some conditions, a 10-Mor larger body can form by...

    • Giant Planet and Brown Dwarf Formation
      (pp. 619-642)
      Gilles Chabrier, Anders Johansen, Markus Janson and Roman Rafikov

      The past decade has seen a wealth of substellar object (SSO) discoveries. Substellar objects are defined as objects not massive enough to sustain hydrogen burning and thus encompass brown dwarfs (BD) and planets, more specifically giant planets (GP), which we will focus on in the present review. For the sake of clarity, we will first specify which objects we refer to as “brown dwarfs” and “giant planets,” respectively. For reasons that will be detailed in this review, we do not use the International Astronomical Union (IAU) definition to distinguish between these two populations. Instead, we adopt a classification that, as...

    • Giant Planet Formation, Evolution, and Internal Structure
      (pp. 643-666)
      Ravit Helled, Peter Bodenheimer, Morris Podolak, Aaron Boley, Farzana Meru, Sergei Nayakshin, Jonathan J. Fortney, Lucio Mayer, Yann Alibert and Alan P. Boss

      Giant planets play a critical role in shaping the architectures of planetary systems. Their large masses, orbital angular momentum, and fast formation make them prime candidates for driving rich dynamics among nascent planets, including exciting the orbits of small bodies and possibly delivering volatiles to terrestrial planets. Their bulk properties are also key for exploring the physical and chemical conditions of protoplanetary disks in which planets form. Furthermore, the diversity in properties (e.g., mass, radius, semimajor axis, and density) of exoplanets calls for multiple formation and evolution mechanisms to be explored. As a result, detailed investigations of the formation mechanism,...

    • Planet-Disk Interactions and Early Evolution of Planetary Systems
      (pp. 667-690)
      Clément Baruteau, Aurélien Crida, Sijme-Jan Paardekooper, Frédéric Masset, Jérôme Guilet, Bertram Bitsch, Richard Nelson, Wilhelm Kley and John Papaloizou

      Since the fifth edition of Protostars and Planets in 2005 (PPV) (seeReipurth et al., 2007), the number of extrasolar planets has increased from about 200 to nearly 1000, with several thousand transiting planet candidates awaiting confirmation. These prolific discoveries have emphasized the amazing diversity of exoplanetary systems. They have brought crucial constraints on models of planet formation and evolution, which need to account for the many flavors in which exoplanets come. Some giant planets, widely known as the hot Jupiters, orbit their star in just a couple of days, like 51 Pegasus b (Mayor and Queloz, 1995). Some others...

    • Planet Population Synthesis
      (pp. 691-714)
      Willy Benz, Shigeru Ida, Yann Alibert, Douglas Lin and Christoph Mordasini

      The number of known exoplanets has increased dramatically in recent years (seewww.exoplanet.eu). As of this writing, over 1000 confirmed exoplanets were known, mostly found through precise radial velocity (RV) surveys. Additionally, there are more than 3600 transiting candidate planets found by the Kepler satellite (see, e.g.,www.kepler.nasa.gov). All these detections have revealed that planets are quite common and that the diversity of existing systems is much larger than was expected from studies of our own solar system. Finally, with the increasing number of planets, the search for correlations and structures in the properties of planets and planetary systems becomes...

    • Exoplanet Detection Techniques
      (pp. 715-738)
      Debra A. Fischer, Andrew W. Howard, Greg P. Laughlin, Bruce Macintosh, Suvrath Mahadevan, Johannes Sahlmann and Jennifer C. Yee

      Humans have long wondered whether other solar systems exist around the billions of stars in our galaxy. In the past two decades, we have progressed from a sample of one to a collection of hundreds of exoplanetary systems. Instead of an orderly solar nebula model, we now realize that chaos rules the formation of planetary systems. Gas giant planets can migrate close to their stars. Small rocky planets are abundant and dynamically pack the inner orbits. Planets circle outside the orbits of binary star systems. The diversity is astonishing.

      Several methods for detecting exoplanets have been developed: Doppler measurements, transit...

    • Exoplanetary Atmospheres
      (pp. 739-762)
      Nikku Madhusudhan, Heather Knutson, Jonathan J. Fortney and Travis Barman

      The study of exoplanetary atmospheres is at the center of the new era of exoplanet science. About 800 confirmed exoplanets, and over 3000 candidates, are now known. The last two decades in exoplanet science have provided exquisite statistics on the census of exoplanets in the solar neighborhood and their macroscopic properties, which include orbital parameters (eccentricities, separations, periods, spin-orbit alignments, multiplicity, etc.), bulk parameters (masses, radii, equilibrium temperatures), and properties of their host stars. The sum total of current knowledge has taught us that exoplanets are extremely diverse in all these macroscopic physical parameters. We are now entering a new...

    • Planetary Internal Structures
      (pp. 763-786)
      Isabelle Baraffe, Gilles Chabrier, Jonathan Fortney and Christophe Sotin

      The 1990s were marked by two historical discoveries: the first planetary system around a star other than the Sun, namely a pulsar (Wolszczan and Frail, 1992), and the first Jupiter-mass companion to a solar-type star (Mayor and Queloz, 1995). Before that, the development and application of planetary structure theory was restricted to the few planets belonging to our solar system. Planetary interiors provide natural laboratories to study materials under high pressure, complementing experiments that can be done on Earth. This explains why planets have long been of interest to physicists studying the equations of state (EOS) of hydrogen, helium, and...

    • The Long-Term Dynamical Evolution of Planetary Systems
      (pp. 787-808)
      Melvyn B. Davies, Fred C. Adams, Philip Armitage, John Chambers, Eric Ford, Alessandro Morbidelli, Sean N. Raymond and Dimitri Veras

      Currently observed planetary systems have typically evolved between the time when the last gas in the protoplanetary disk was dispersed and today. The clearest evidence for this assertion comes from the distribution of Kuiper belt objects in the outer solar system, and from the eccentricities of massive extrasolar planets, but many other observed properties of planetary systems may also plausibly be the consequence of dynamical evolution. This chapter summarizes the different types of gravitational interactions that lead to long-term evolution of planetary systems, and reviews the application of theoretical models to observations of the solar system and extrasolar planetary systems....

    • Samples of the Solar System: Recent Developments
      (pp. 809-832)
      Andrew M. Davis, Conel M. O’D. Alexander, Fred J. Ciesla, Matthieu Gounelle, Alexander N. Krot, Michail I. Petaev and Thomas Stephan

      The seven years since publication ofProtostars and Planets V(Reipurth et al., 2007) have seen a number of major discoveries about the chemistry and physics of the solar system and other stars based on the laboratory study of samples returned to Earth by spacecraft and by nature (i.e., meteorites and interplanetary dust particles). In this chapter, we highlight some of the more important discoveries and their implications.

      The Genesis mission, which returned samples of the solar wind to Earth in 2004, has provided two very surprising results: that the solar wind, and by inference, the Sun, is significantly different...

  8. PART IV: ASTROPHYSICAL CONDITIONS FOR LIFE
    • Water: From Clouds to Planets
      (pp. 835-858)
      Ewine F. van Dishoeck, Edwin A. Bergin, Dariusz C. Lis and Jonathan I. Lunine

      With nearly 1000 exoplanets discovered to date and statistics indicating that every star hosts at least one planet (Batalha et al., 2013), the next step in our search for life elsewhere in the universe is to characterize these planets. The presence of water on a planet is universally accepted as essential for its potential habitability. Water in gaseous form acts as a coolant that allows interstellar gas clouds to collapse to form stars, whereas water ice facilitates the sticking of small dust particles that eventually must grow to planetesimals and planets. The development of life requires liquid water, and even...

    • Deuterium Fractionation: The Ariadne’s Thread from the Precollapse Phase to Meteorites and Comets Today
      (pp. 859-882)
      Cecilia Ceccarelli, Paola Caselli, Dominique Bockelée-Morvan, Olivier Mousis, Sandra Pizzarello, Francois Robert and Dmitry Semenov

      The ancient Greek legend reads that Theseus volunteered to enter the Minotaur’s labyrinth to kill the monster and liberate Athens from having to periodically sacrifice young women and men. The task was almost impossible to achieve because killing the Minotaur was not even half the problem; getting out of the labyrinth was even more difficult. But Ariadne, the guardian of the labyrinth and daughter of the king of Crete, provided Theseus with a ball of thread, so he could unroll it when entering the labyrinth and then follow it back to find his way out — which he did.

      Our...

    • Astrophysical Conditions for Planetary Habitability
      (pp. 883-906)
      Manuel Güdel, Rudolf Dvorak, Nikolai Erkaev, James Kasting, Maxim Khodachenko, Helmut Lammer, Elke Pilat-Lohinger, Heike Rauer, Ignasi Ribas and Brian E. Wood

      Discovery of planets around other stars is now well underway. Over 1000 extrasolar planets have been found mainly by groundbased radial velocity (RV) measurements and space- and groundbased photometric transit surveys (exoplanets.org). In addition, ≈3500 “planet candidates” have been found by Kepler (Batalha et al., 2013) (updates as of November 2013). Due to instrument sensitivity the first planets detected were predominantly gas or ice giants, like Jupiter or Neptune. Recent work byHoward(2013) andFressin et al. (2013) show that small transiting planets are more numerous than big ones. Some potentially rocky planets have been identified (Léger et al.,...

  9. Index
    (pp. 907-914)