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713 results on '"Guillot , Tristan"'

252. Observation scheduling and automatic data reduction for the Antarctic Telescope, ASTEP+

Author

Adler, David S., Seaman, Robert L., Benn, Chris R., Dransfield, Georgina, Mékarnia, Djamel, Triaud, Amaury H. M. J., Guillot, Tristan, Abe, Lyu, García, Lionel J., Timmermans, Mathilde, Crouzet, Nicolas, Schmider, François-Xavier, Agabi, Abdelkarim, Suarez, Olga, Bendjoya, Philippe, Guenther, Maximilian N., Lai, Olivier, Merin, Bruno, and Stee, Philippe

Published
2022
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253. Mechanisms affecting the composition of Hot Jupiters atmospheres

Author

Showman Adam P., Guillot Tristan, and Parmentier Vivien

Subjects
Physics, QC1-999
Abstract

Opacities and thus local chemical composition play a key role when characterizing exoplanet atmospheres from observations. When the gas is in chemical equilibrium the chemical abundances depend strongly on the temperature profile. Grey models tend to overestimate the temperatures in the upper atmosphere. We present a new analytical model with a more realistic description of the radiative cooling in the infrared. Mechanisms like quenching and cold traps can drive the upper atmosphere far from its chemical equilibrium. The efficiency of these mechanisms depends on the strength of the vertical mixing. Using 3D global circulation models of HD209458b including passive tracers, we show that, although Hot Jupiter atmospheres are stably stratified, they are strongly mixed by planetary scale circulation patterns. We provide a rough estimate of the effective vertical mixing coefficient in Hot Jupiter atmosphere which can be used in 1D models.

Published
2013
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254. In Situ Exploration of the Giant Planets In Situ Exploration of the Giant Planets

Author

Mousis, Olivier, Atkinson, David H., Ambrosi, Richard, Atreya, Sushil, Banfield, Don, Barabash, Stas, Blanc, Michel, Cavalié, Thibault, Coustenis, Athena, Durry, Georges, Ferri, Francesca, Fletcher, Leigh, Fouchet, Thierry, Guillot, Tristan, Hartogh, Paul, Hueso, Ricardo, Hofstadter, Mark, Lebreton, Jean-Pierre, Mandt, Kathleen, Rauer, Heike, Rannou, Pascal, Jean-Baptiste Renard, Sanchez-Lavega, Agustin, Sayanagi, Kunio, Simon, Amy A., Spilker, Thomas, Ethiraj Venkatapathy, J. Hunter Waite, and Wurz, Peter

Published
2019
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257. Recent results from the imagery of Juno’s Stellar Reference Unit

Author

Becker, Heidi, primary, Alexander, James, additional, Atreya, Sushil, additional, Bolton, Scott, additional, Brennan, Martin, additional, Brown, Shannon, additional, Florence, Meghan, additional, Guillaume, Alexandre, additional, Guillot, Tristan, additional, Ingersoll, Andrew, additional, Levin, Steven, additional, Lunine, Jonathan, additional, Steffes, Paul, additional, and Aglyamov, Youry, additional

Published
2020
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259. The water abundance in Jupiter’s equatorial zone

Author

Li, Cheng, primary, Ingersoll, Andrew, additional, Bolton, Scott, additional, Levin, Steven, additional, Janssen, Michael, additional, Atreya, Sushil, additional, Lunine, Jonathan, additional, Steffes, Paul, additional, Brown, Shannon, additional, Guillot, Tristan, additional, Allison, Michael, additional, Arballo, John, additional, Bellotti, Amadeo, additional, Adumitroaie, Virgil, additional, Gulkis, Samuel, additional, Hodges, Amoree, additional, Li, Liming, additional, Misra, Sidharth, additional, Orton, Glenn, additional, Oyafuso, Fabiano, additional, Santos-Costa, Daniel, additional, Waite, Hunter, additional, and Zhang, Zhimeng, additional

Published
2020
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261. First measurements of the Jovian zonal winds profile through visible Doppler spectroscopy

Author

Schmider, François-Xavier, Gonçalves, Ivan, Gaulme, Patrick, Morales-Juberias, Raùl, Guillot, Tristan, Rivet, Jean-Pierre, Appourchaux, Thierry, Boumier, Patrick, Jackiewicz, Jason, Underwood, Thomas, Voelz, David, Sato, Bun’ei, Ida, Shigeru, Ikoma, Masahiro, Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Max Planck Inst Sonnensyst Forsch, Gottingen, Germany, New Mexico Institute of Mining and Technology [New Mexico Tech] (NMT), Institut d'astrophysique spatiale (IAS), Université Paris-Sud - Paris 11 (UP11)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), NMSU, Dept Astron, Las Cruces, NM USA, Department of Mechanical and Aerospace Engineering [Las Cruces], New Mexico State University, Global Edge Institute, Tokyo Institute of Technology [Tokyo] (TITECH), and ANR-15-CE31-0014,JOVIAL,Jupiter : Oscillations en Vitesse radiale par ImAgerie multi Longitudes(2015)

Subjects
Physics::Space Physics, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics, Physics::Atmospheric and Oceanic Physics
Abstract

International audience; We present the first measurements of Jupiter's wind profile obtained from radial-velocity measurements. Radial velocity measurements of wind are rather difficult, but can be very interesting as they measure the actual speed of cloud particles instead of the motion of large cloud structures. Here we present the first scientific results of the Doppler spectro-imager JOVIAL-JIVE, dedicated to giant planets' seismology and atmospheric dynamics. The instrument provides instantaneous velocity maps in the mid-visible domain by monitoring the Doppler shift of solar Fraunhofer lines reflected in the planets' upper atmosphere thanks to an imaging Fourier transform spectrometer. We present profiles of the zonal wind speed of Jupiter as function of latitude from observations obtained between 2015 and 2017. Our results are compared with wind profiles obtained by cloud tracking from HST images at the same epoch. We point out comparable results from both techniques except at the latitude of the hot spots in the northern equatorial band (≈ 5 • N) where we find a much lower wind speed.

Published
2018

262. SPRITE (Saturn PRobe Interior and aTmosphere Explorer): A Saturn Entry Probe Mission Concept

Author

Atkinson, David H., Simon, Amy, Banfield, Don, Atreya, Sushil, Blacksberg, Jordana, Brinckerhoff, Will, Colaprete, Anthony, Coustenis, Athena, Fletcher, Leigh, Guillot, Tristan, Hofstadter, Mark, Lunine, Jonathan, Mahaffy, Paul, Marley, Mark, Mousis, Olivier, Spilker, Thomas, Trainer, Melissa, Webster, Chris, NASA Goddard Space Flight Center (GSFC), Cornell University [New York], University of Michigan [Ann Arbor], University of Michigan System, NASA Ames Research Center (ARC), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), University of Leicester, Laboratoire de Cosmologie, Astrophysique Stellaire & Solaire, de Planétologie et de Mécanique des Fluides (CASSIOPEE), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Lunar and Planetary Laboratory [Tucson] (LPL), University of Arizona, GSFC Solar System Exploration Division, Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), and Université Nice Sophia Antipolis (1965 - 2019) (UNS)

Subjects
[SDU]Sciences of the Universe [physics]
Abstract

International audience; A Saturn entry probe mission concept is presented for in situ studies of the Saturn atmospheric composition, structure, and dynamics to a depth of 10 bars or greater.

Published
2018

263. Evidence for an additional planet in the β Pictoris system

Author

Lagrange, A.-M., primary, Meunier, Nadège, additional, Rubini, Pascal, additional, Keppler, Miriam, additional, Galland, Franck, additional, Chapellier, Eric, additional, Michel, Eric, additional, Balona, Luis, additional, Beust, Hervé, additional, Guillot, Tristan, additional, Grandjean, Antoine, additional, Borgniet, Simon, additional, Mékarnia, Djamel, additional, Wilson, Paul Anthony, additional, Kiefer, Flavien, additional, Bonnefoy, Mickael, additional, Lillo-Box, Jorge, additional, Pantoja, Blake, additional, Jones, Matias, additional, Iglesias, Daniela Paz, additional, Rodet, Laetitia, additional, Diaz, Matias, additional, Zapata, Abner, additional, Abe, Lyu, additional, and Schmider, François-Xavier, additional

Published
2019
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265. Uranus and Neptune: Origin, Evolution and Internal Structure

Author

Helled, Ravit, Nettelmann, Nadine, Guillot, Tristan, Helled, Ravit, Nettelmann, Nadine, and Guillot, Tristan

Abstract

There are still many open questions regarding the nature of Uranus and Neptune, the outermost planets in the Solar System. In this review we summarize the current-knowledge about Uranus and Neptune with a focus on their composition and internal structure, formation including potential subsequent giant impacts, and thermal evolution. We present key open questions and discuss the uncertainty in the internal structures of the planets due to the possibility of non-adiabatic and inhomogeneous interiors. We also provide the reasoning for improved observational constraints on their fundamental physical parameters such as their gravitational and magnetic fields, rotation rates, and deep atmospheric composition and temperature. Only this way will we be able to improve our understating of these planetary objects, and the many similar-sized objects orbiting other stars., Comment: Accepted for publication in Space Science Reviews

Published
2019
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266. In situ Exploration of the Giant Planets

Author

Mousis, Olivier, Atkinson, David H., Ambrosi, Richard, Atreya, Sushil, Banfield, Don, Barabash, Stas, Blanc, Michel, Cavalié, Thibault, Coustenis, Athena, Deleuil, Magali, Durry, Georges, Ferri, Francesca, Fletcher, Leigh, Fouchet, Thierry, Guillot, Tristan, Hartogh, Paul, Hueso, Ricardo, Hofstadter, Mark, Lebreton, Jean-Pierre, Mandt, Kathleen E., Rauer, Heike, Rannou, Pascal, Renard, Jean-Baptiste, Sanchez-Lávega, Agustin, Sayanagi, Kunio, Simon, Amy, Spilker, Thomas, Venkatapathy, Ethiraj, Waite, J. Hunter, Wurz, Peter, Mousis, Olivier, Atkinson, David H., Ambrosi, Richard, Atreya, Sushil, Banfield, Don, Barabash, Stas, Blanc, Michel, Cavalié, Thibault, Coustenis, Athena, Deleuil, Magali, Durry, Georges, Ferri, Francesca, Fletcher, Leigh, Fouchet, Thierry, Guillot, Tristan, Hartogh, Paul, Hueso, Ricardo, Hofstadter, Mark, Lebreton, Jean-Pierre, Mandt, Kathleen E., Rauer, Heike, Rannou, Pascal, Renard, Jean-Baptiste, Sanchez-Lávega, Agustin, Sayanagi, Kunio, Simon, Amy, Spilker, Thomas, Venkatapathy, Ethiraj, Waite, J. Hunter, and Wurz, Peter

Abstract

Remote sensing observations suffer significant limitations when used to study the bulk atmospheric composition of the giant planets of our solar system. This impacts our knowledge of the formation of these planets and the physics of their atmospheres. A remarkable example of the superiority of in situ probe measurements was illustrated by the exploration of Jupiter, where key measurements such as the determination of the noble gases' abundances and the precise measurement of the helium mixing ratio were only made available through in situ measurements by the Galileo probe. Here we describe the main scientific goals to be addressed by the future in situ exploration of Saturn, Uranus, and Neptune, placing the Galileo probe exploration of Jupiter in a broader context. An atmospheric entry probe targeting the 10-bar level would yield insight into two broad themes: i) the formation history of the giant planets and that of the Solar System, and ii) the processes at play in planetary atmospheres. The probe would descend under parachute to measure composition, structure, and dynamics, with data returned to Earth using a Carrier Relay Spacecraft as a relay station. An atmospheric probe could represent a significant ESA contribution to a future NASA New Frontiers or flagship mission to be launched toward Saturn, Uranus, and/or Neptune., Comment: 27 pages, 9 figures, White Paper submitted in response to ESA's Call for Voyage 2050 Science Themes. arXiv admin note: substantial text overlap with arXiv:1708.00235

Published
2019

267. Comparison of the deep atmospheric dynamics of Jupiter and Saturn in light of the Juno and Cassini gravity measurements

Author

Kaspi, Yohai, Galanti, Eli, Showman, Adam P., Stevenson, David J., Guillot, Tristan, Iess, Luciano, Bolton, Scott J., Kaspi, Yohai, Galanti, Eli, Showman, Adam P., Stevenson, David J., Guillot, Tristan, Iess, Luciano, and Bolton, Scott J.

Abstract

The nature and structure of the observed east-west flows on Jupiter and Saturn has been one of the longest-lasting mysteries in planetary science. This mystery has been recently unraveled due to the accurate gravity measurements provided by the Juno mission to Jupiter and the Grand Finale of the Cassini mission to Saturn. These two experiments, which coincidentally happened around the same time, allowed determination of the vertical and meridional profiles of the zonal flows on both planets. This paper reviews the topic of zonal jets on the gas giants in light of the new data from these two experiments. The gravity measurements not only allow the depth of the jets to be constrained, yielding the inference that the jets extend roughly 3000 and 9000 km below the observed clouds on Jupiter and Saturn, respectively, but also provide insights into the mechanisms controlling these zonal flows. Specifically, for both planets this depth corresponds to the depth where electrical conductivity is within an order of magnitude of 1 S/m, implying that the magnetic field likely plays a key role in damping the zonal flows., Comment: Submitted to Space Science Reviews. Part of ISSI special collection on Diversity of Atmospheres

Published
2019
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268. Uranus and Neptune are key to understand planets with hydrogen atmospheres

Author

Guillot, Tristan and Guillot, Tristan

Abstract

Uranus and Neptune are the last unexplored planets of the Solar System. I show that they hold crucial keys to understand the atmospheric dynamics and structure of planets with hydrogen atmospheres. Their atmospheres are active and storms are believed to be fueled by methane condensation which is both extremely abundant and occurs at low optical depth. This means that mapping temperature and methane abundance as a function of position and depth will inform us on how convection organizes in an atmosphere with no surface and condensates that are heavier than the surrounding air, a general feature of gas giants. Using this information will be essential to constrain the interior structure of Uranus and Neptune themselves, but also of Jupiter, Saturn and numerous exoplanets with hydrogen atmospheres. Owing to the spatial and temporal variability of these atmospheres, an orbiter is required. A probe would provide a reference profile to lift ambiguities inherent to remote observations. It would also measure abundances of noble gases which can be used to reconstruct the history of planet formation in the Solar System. Finally, mapping the planets' gravity and magnetic fields will be essential to constrain their global composition, structure and evolution.

Published
2019
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269. How well do we understand the belt/zone circulation of Giant Planet atmospheres?

Author

Fletcher, Leigh N., Kaspi, Yohai, Guillot, Tristan, Showman, Adam P., Fletcher, Leigh N., Kaspi, Yohai, Guillot, Tristan, and Showman, Adam P.

Abstract

The atmospheres of the four giant planets of our Solar System share a common and well-observed characteristic: they each display patterns of planetary banding, with regions of different temperatures, composition, aerosol properties and dynamics separated by strong meridional and vertical gradients in the zonal (i.e., east-west) winds. On Jupiter, the reflective white bands of low temperatures, elevated aerosol opacities, and enhancements of quasi-conserved chemical tracers are referred to as 'zones.' Conversely, the darker bands of warmer temperatures, depleted aerosols, and reductions of chemical tracers are known as `belts.' On Saturn, we define cyclonic belts and anticyclonic zones via their temperature and wind characteristics, although their relation to Saturn's albedo is not as clear as on Jupiter. On distant Uranus and Neptune, the exact relationships between the banded albedo contrasts and the environmental properties is a topic of active study. This review is an attempt to reconcile the observed properties of belts and zones with (i) the meridional overturning inferred from the convergence of eddy angular momentum into the eastward zonal jets at the cloud level on Jupiter and Saturn and the prevalence of moist convective activity in belts; and (ii) the opposing meridional motions inferred from the upper tropospheric temperature structure, which implies decay and dissipation of the zonal jets with altitude above the clouds. These two scenarios suggest meridional circulations in opposing directions, the former suggesting upwelling in belts, the latter suggesting upwelling in zones. This presents an unresolved paradox for our current understanding of the banded structure of giant planet atmospheres, that could be addressed via a multi-tiered vertical structure of 'stacked circulation cells.' [Abridged], Comment: 25 pages, 6 figures, Space Science Reviews, accepted

Published
2019
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270. Saturn's deep atmospheric flows revealed by the Cassini Grand Finale gravity measurements

Author

Galanti, Eli, Kaspi, Yohai, Miguel, Yamila, Guillot, Tristan, Durante, Daniele, Racioppa, Paolo, Iess, Luciano, Galanti, Eli, Kaspi, Yohai, Miguel, Yamila, Guillot, Tristan, Durante, Daniele, Racioppa, Paolo, and Iess, Luciano

Abstract

How deep do Saturn's zonal winds penetrate below the cloud-level has been a decades-long question, with important implications not only for the atmospheric dynamics, but also for the interior density structure, composition, magnetic field and core mass. The Cassini Grand Finale gravity experiment enables answering this question for the first time, with the premise that the planet's gravity harmonics are affected not only by the rigid body density structure but also by its flow field. Using a wide range of rigid body interior models and an adjoint based thermal wind balance, we calculate the optimal flow structure below the cloud-level and its depth. We find that with a wind profile, largely consistent with the observed winds, when extended to a depth of around 8,800 km, all the gravity harmonics measured by Cassini are explained. This solution is in agreement with considerations of angular momentum conservation, and is consistent with magnetohydrodynamics constraints.

Published
2019
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271. Scientific rationale and concepts for in situ probe exploration of Uranus and Neptune

Author

Mousis, Olivier, Atkinson, David, Cavalié, T., Fletcher, Leigh, Amato, Michael, Aslam, Shahid, Ferri, Francesca, Renard, Jean-Baptiste, Spilker, Thomas, Venkatapathy, Ethiraj, Wurz, Peter, Aplin, Karen, Coustenis, Athena, Deleuil, Magali, Dobrijevic, M., Fouchet, Thierry, Guillot, Tristan, Hartogh, Paul, Hewagama, Tilak, Hofstadter, Mark, Univers, Transport, Interfaces, Nanostructures, Atmosphère et environnement, Molécules (UMR 6213) (UTINAM), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC), Center for medical imaging, University College of London [London] (UCL), Environnement et Grandes Cultures (EGC), Institut National de la Recherche Agronomique (INRA)-AgroParisTech, Department of Atmospheric, Oceanic, and Space Sciences [Ann Arbor] (AOSS), University of Michigan [Ann Arbor], University of Michigan System-University of Michigan System, University of Oxford, Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), ASP 2017, Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), Max-Planck-Gesellschaft, Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Escuela Tecnica Superior de Ingenieria Bilbao, Centre for Medical Imaging, University College London, London, United Kingdom, ASP 2018, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), University of Leicester, NASA Goddard Space Flight Center (GSFC), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Physikalisches Institut [Bern], Universität Bern [Bern], Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Centre National d'Études Spatiales [Toulouse] (CNES), Laboratoire de Cosmologie, Astrophysique Stellaire & Solaire, de Planétologie et de Mécanique des Fluides (CASSIOPEE), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Max-Planck-Institut für Sonnensystemforschung (MPS), Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), University of Oxford [Oxford], Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), California Institute of Technology (CALTECH)-NASA, Universität Bern [Bern] (UNIBE), AgroParisTech-Institut National de la Recherche Agronomique (INRA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur, and COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics::Space Physics, Astrophysics::Instrumentation and Methods for Astrophysics, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Physics::Atmospheric and Oceanic Physics
Abstract

International audience; Uranus and Neptune, referred to as ice giants, are fundamentally different from the better-known gas giants (Jupiter and Saturn). Exploration of an ice giant system is a high-priority science objective, as these systems (including the magnetosphere, satellites, rings, atmosphere, and interior) challenge our understanding of planetary formation and evolution. The importance of the ice giants is reflected in NASA's 2011 Decadal Survey, comments from ESA's SSC in response to L2/L3 mission proposals and results of the 2017 NASA/ESA Ice Giants study. A crucial part of exploration of the ice giants is in situ sampling of the atmosphere via an atmospheric probe. A probe would bring insights in two broad themes: the formation history of our Solar System and the processes at play in planetary atmospheres. Here we summarize the science driver for in situ measurements at these two planets and discuss possible mission concepts that would be consistent with the constraints of ESA M-class missions.

Published
2017

272. Internal Structure of Giant and Icy Planets: Importance of Heavy Elements and Mixing

Author

Helled, Ravit and Guillot, Tristan

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), FOS: Physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract

In this chapter we summarize current knowledge of the internal structure of giant planets. We concentrate on the importance of heavy elements and their role in determining the planetary composition and internal structure, in planet formation, and during the planetary long-term evolution. We briefly discuss how internal structure models are derived, present the possible structures of the outer planets in the Solar System, and summarise giant planet formation and evolution. Finally, we introduce giant exoplanets and discuss how they can be used to better understand giant planets as a class of planetary objects., Invited review chapter, accepted for publication in "Handbook of Exoplanets"

Published
2017

273. First measurements of Jupiter’s zonal winds with visible imaging spectroscopy

Author

Gonçalves, Ivan, primary, Schmider, F.X., additional, Gaulme, Patrick, additional, Morales-Juberías, Raúl, additional, Guillot, Tristan, additional, Rivet, Jean-Pierre, additional, Appourchaux, Thierry, additional, Boumier, Patrick, additional, Jackiewicz, Jason, additional, Sato, Bun’ei, additional, Ida, Shigeru, additional, Ikoma, Masahiro, additional, Mékarnia, Djamel, additional, Underwood, Thomas A, additional, and Voelz, David, additional

Published
2019
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274. Small lightning flashes from shallow electrical storms on Jupiter.

Author

Becker, Heidi N., Alexander, James W., Atreya, Sushil K., Bolton, Scott J., Brennan, Martin J., Brown, Shannon T., Guillaume, Alexandre, Guillot, Tristan, Ingersoll, Andrew P., Levin, Steven M., Lunine, Jonathan I., Aglyamov, Yury S., and Steffes, Paul G.

Abstract

Lightning flashes have been observed by a number of missions that visited or flew by Jupiter over the past several decades. Imagery led to a flash rate estimate of about 4 × 10−3 flashes per square kilometre per year (refs. 1,2). The spatial extent of Voyager flashes was estimated to be about 30 kilometres (half-width at half-maximum intensity, HWHM), but the camera was unlikely to have detected the dim outer edges of the flashes, given its weak response to the brightest spectral line of Jovian lightning emission, the 656.3-nanometre Hα line of atomic hydrogen1,3–6. The spatial resolution of some cameras allowed investigators to confirm 22 flashes with HWHM greater than 42 kilometres, and to estimate one with an HWHM of 37 to 45 kilometres (refs. 1,7–9). These flashes, with optical energies comparable to terrestrial 'superbolts'—of (0.02–1.6) × 1010 joules—have been interpreted as tracers of moist convection originating near the 5-bar level of Jupiter's atmosphere (assuming photon scattering from points beneath the clouds)1–3,7,8,10–12. Previous observations of lightning have been limited by camera sensitivity, distance from Jupiter and long exposures (about 680 milliseconds to 85 seconds), meaning that some measurements were probably superimposed flashes reported as one1,2,7,9,10,13. Here we report optical observations of lightning flashes by the Juno spacecraft with energies of approximately 105–108 joules, flash durations as short as 5.4 milliseconds and inter-flash separations of tens of milliseconds, with typical terrestrial energies. The flash rate is about 6.1 × 10−2 flashes per square kilometre per year, more than an order of magnitude greater than hitherto seen. Several flashes are of such small spatial extent that they must originate above the 2-bar level, where there is no liquid water14,15. This implies that multiple mechanisms for generating lightning on Jupiter need to be considered for a full understanding of the planet's atmospheric convection and composition. Small lightning flashes detected on Jupiter by Juno have shallow origins above the 2-bar level of Jupiter's atmosphere where temperatures are too low for liquid water to exist. [ABSTRACT FROM AUTHOR]

Published
2020
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275. Comparison of the Deep Atmospheric Dynamics of Jupiter and Saturn in Light of the Juno and Cassini Gravity Measurements.

Author

Kaspi, Yohai, Galanti, Eli, Showman, Adam P., Stevenson, David J., Guillot, Tristan, Iess, Luciano, and Bolton, Scott J.

Subjects
GRAVIMETRY, ATMOSPHERIC circulation, PLANETARY science, GAS giants, JUPITER (Planet), ELECTRIC conductivity, ROSSBY waves
Abstract

The nature and structure of the observed east-west flows on Jupiter and Saturn have been a long-standing mystery in planetary science. This mystery has been recently unraveled by the accurate gravity measurements provided by the Juno mission to Jupiter and the Grand Finale of the Cassini mission to Saturn. These two experiments, which coincidentally happened around the same time, allowed the determination of the overall vertical and meridional profiles of the zonal flows on both planets. This paper reviews the topic of zonal jets on the gas giants in light of the new data from these two experiments. The gravity measurements not only allow the depth of the jets to be constrained, yielding the inference that the jets extend to roughly 3000 and 9000 km below the observed clouds on Jupiter and Saturn, respectively, but also provide insights into the mechanisms controlling these zonal flows. Specifically, for both planets this depth corresponds to the depth where electrical conductivity is within an order of magnitude of 1 S m−1, implying that the magnetic field likely plays a key role in damping the zonal flows. An intrinsic characteristic of any gravity inversion, as discussed here, is that the solutions might not be unique. We analyze the robustness of the solutions and present several independent lines of evidence supporting the results presented here. [ABSTRACT FROM AUTHOR]

Published
2020
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277. Revisiting the pre-main-sequence evolution of stars II. Consequences of planet formation on stellar surface composition

Author

Kunitomo, Masanobu, Guillot, Tristan, Ida, Shigeru, Takeuchi, Taku, Kunitomo, Masanobu, Guillot, Tristan, Ida, Shigeru, and Takeuchi, Taku

Abstract

We want to investigate how planet formation is imprinted on stellar surface composition using up-to-date stellar evolution models. We simulate the evolution of pre-main-sequence stars as a function of the efficiency of heat injection during accretion, the deuterium mass fraction, and the stellar mass. For simplicity, we assume that planet formation leads to the late accretion of zero-metallicity gas, diluting the surface stellar composition as a function of the mass of the stellar outer convective zone. We adopt $150\,{\mathrm{M}_\oplus}(M_\star/\mathrm{M}_\odot)(Z/\mathrm{Z}_\odot)$ as an uncertain but plausible estimate of the mass of heavy elements that is not accreted by stars with giant planets, including our Sun. By combining our stellar evolution models to these estimates, we evaluate the consequences of planet formation on stellar surface composition. We show that after the first $\sim0.1$ Myr, the evolution of the convective zone follows classical evolutionary tracks within a factor of two in age. We find that planet formation should lead to a scatter in stellar surface composition that is larger for high-mass stars than for low-mass stars. We predict a spread in [Fe/H] of approximately $0.02$ dex for stars with $T_\mathrm{eff}\sim 5500\,$K, marginally compatible with differences in metallicities observed in some binary stars with planets. Stars with $T_\mathrm{eff}\geq 7000\,$K may show much larger [Fe/H] deficits, by 0.6 dex or more, compatible with the existence of refractory-poor $\lambda$ Boo stars. We also find that planet formation may explain the lack of refractory elements seen in the Sun as compared to solar twins, but only if the ice-to-rock ratio in the solar-system planets is less than $\approx0.4$ and planet formation began less than $\approx1.3$ Myr after the beginning of the formation of the Sun. (abbreviated), Comment: Accepted for publicatoin in A&A. 18 pages, 14 figures

Published
2018
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278. An Analysis of Stochastic Jovian Oscillation Excitation by Moist Convection

Author

Dederick, Ethan, Jackiewicz, Jason, Guillot, Tristan, Dederick, Ethan, Jackiewicz, Jason, and Guillot, Tristan

Abstract

Recent observations of Jupiter have suggested the existence of global oscillatory modes at millihertz frequencies, yet the source mechanism responsible for driving these modes is still unknown. However, the energies necessary to produce observable surface oscillations have been predicted. Here we investigate if moist convection in Jupiter's upper atmosphere can be responsible for driving the global oscillations and what moist convective energy requirements are necessary to achieve these theoretical mode energies and surface amplitudes. We begin by creating a one-dimensional moist convective cloud model and find that the available kinetic energy of the rising cloud column falls below theoretical estimates of oscillations energies. That is, mode excitation cannot occur with a single storm eruption. We then explore stochastic excitation scenarios of the oscillations by moist convective storms. We find that mode energies and amplitudes can reach theoretical estimates if the storm energy available to the modes is more than just kinetic. In order for the modes to be excited, we find that they require $5 \times 10^{27}$ to 10$^{28}$ erg per day. However, even for a large storm eruption each day, the available kinetic energy from the storms falls two orders of magnitude short of the required driving energy. Although our models may oversimplify the true complexity of the coupling between Jovian storms and global oscillations, our findings reveal that enough thermal energy is associated with moist convection to drive the modes, should it be available to them.

Published
2018
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279. Jupiter’s evolution with primordial composition gradients

Author

Vazan, Allona, Helled, Ravit, Guillot, Tristan, Vazan, Allona, Helled, Ravit, and Guillot, Tristan

Abstract

Recent formation and structure models of Jupiter suggest that the planet can have composition gradients and not be fully convective (adiabatic). This possibility directly affects our understanding of Jupiter’s bulk composition and origin. In this Letter we present Jupiter’s evolution with a primordial structure consisting of a relatively steep heavy-element gradient of 40 M⊕. We show that for a primordial structure with composition gradients, most of the mixing occurs in the outer part of the gradient during the early evolution (several 107 yr), leading to an adiabatic outer envelope (60% of Jupiter’s mass). We find that the composition gradient in the deep interior persists, suggesting that ~40% of Jupiter’s mass can be non-adiabatic with a higher temperature than the one derived from Jupiter’s atmospheric properties. The region that can potentially develop layered convection in Jupiter today is estimated to be limited to ~10% of the mass.

Published
2018

284. The interiors of giant planets: Models and outstanding questions

Author

Guillot, Tristan

Subjects
Planetary science -- Research, Planet formation -- Research, Astronomy, Earth sciences
Abstract

The discovery of giant planets orbiting other stars is an opportunity to learn more about these objects their composition, the way in which these processes influence their structure and evolution and the way they form. The intercomparison of presently characterized extrasolar giant planets shows that they are made of hydrogen and helium, but they either have different amounts of heavy metal elements or different orbital evolutions or both.

Published
2005

285. The Origin and Evolution of Saturn, with Exoplanet Perspective

Author

Atreya, Sushil K., Crida, Aurelien, Guillot, Tristan, Lunine, Jonathan I., Madhusudhan, Nikku, and Mousis, Olivier

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), Physics::Space Physics, Astrophysics::Solar and Stellar Astrophysics, FOS: Physical sciences, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract

Saturn formed beyond the snow line in the primordial solar nebula that made it possible for it to accrete a large mass. Disk instability and core accretion models have been proposed for Saturn's formation, but core accretion is favored on the basis of its volatile abundances, internal structure, hydrodynamic models, chemical characteristics of protoplanetary disk, etc. The observed frequency, properties and models of exoplanets provide additional supporting evidence for core accretion. The heavy elements with mass greater than 4He make up the core of Saturn, but are presently poorly constrained, except for carbon. The C/H ratio is super-solar, and twice that in Jupiter. The enrichment of carbon and other heavy elements in Saturn and Jupiter requires special delivery mechanisms for volatiles to these planets. In this chapter we will review our current understanding of the origin and evolution of Saturn and its atmosphere, using a multi-faceted approach that combines diverse sets of observations on volatile composition and abundances, relevant properties of the moons and rings, comparison with the other gas giant planet, Jupiter, analogies to the extrasolar giant planets, as well as pertinent theoretical models., Comment: 36 pages, 9 figures, 3 tables (Table 1 wide)

Published
2016
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287. Probing the giant planets

Author

Guillot, Tristan

Subjects
Outer planets -- Research, Extrasolar planets -- Research, Physics
Abstract

The study of numerous extrasolar planets, which are discovered over the past few years, is presented. To get a better idea, the closest planets, Jupiter and Saturn are studied in detail.

Published
2004

288. Origin of the ices agglomerated by Comet 67P/Churyumov-Gerasimenko

Author

Mousis, Olivier, Lunine, Jonathan I., Luspay-Kuti, Adrienn, Guillot, Tristan, Marty, Bernard, Wurz, Peter, Ali-Dib, Mohamad, Altwegg, Kathrin, Hässig, Myrtha, Rubin, Martin, Vernazza, Pierre, Waite, Jack H., Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Department of Astronomy [Ithaca], Cornell University [New York], Southwest Research Institute [San Antonio] (SwRI), Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Centre de Recherches Pétrographiques et Géochimiques (CRPG), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Physikalisches Institut [Bern], Universität Bern [Bern] (UNIBE), Center for Space and Habitability (CSH), University of Bern, Univers, Transport, Interfaces, Nanostructures, Atmosphère et environnement, Molécules (UMR 6213) (UTINAM), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC), Space Science Division [San Antonio], American Astronomical Society, and POTHIER, Nathalie

Subjects
[SDU] Sciences of the Universe [physics], [SDU]Sciences of the Universe [physics]
Abstract

International audience; The nature of the icy material accreted by comets during their formation in the outer regions of the protosolar nebula is a major open question in planetary science. Some scenarios of comet formation predict that these bodies agglomerated from clathrates crystallized in the protosolar nebula. Concurrently, alternative scenarios suggest that comets accreted amorphous ice originating from the interstellar cloud. Here we show that the recent N2/CO and Ar/CO ratios measured in the coma of the Jupiter family comet 67P/Churyumov-Gerasimenko by the ROSINA instrument aboard the European Space Agency's Rosetta spacecraft can help disentangling between these two scenarios.

Published
2015

289. A semi-empirical model for magnetic braking of solar-type stars

Author

Ardestani, Leila Sadeghi, Guillot, Tristan, Morel, Pierre, Ardestani, Leila Sadeghi, Guillot, Tristan, and Morel, Pierre

Abstract

We develop new angular momentum evolution models for stars with masses of $0.5$ to $1.6~\rm M_\odot$ and from the pre-main-sequence (\rm PMS) through the end of their main-sequence (\rm MS) lifetime. The parametric models include magnetic braking based on numerical simulations of magnetised stellar winds, mass loss rate prescription, core-envelope decoupling as well as disk locking phenomena. We have also accounted for recent developments in modelling dramatically weakened magnetic braking in stars more evolved than the Sun. We fit the free parameters in our model by comparing model predictions to rotational distributions of a number of stellar clusters as well as individual field stars. Our model reasonably successfully reproduces the rotational behaviour of stars during the \rm PMS phase to the zero-age main-sequence (\rm ZAMS) spin up, sudden \rm ZAMS spin down, and convergence of the rotation rates afterwards. We find that including core-envelope decoupling improves our models especially for low-mass stars at younger ages. In addition, by accounting for the almost complete suppression of magnetic braking at slow spin periods, we provide better fits to observations of stellar rotations compared to previous models., Comment: 18 pages, 13 figures, 4 tables, Monthly Notices of the Royal Astronomical Society, stx2039

Published
2017
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290. Revisiting the pre-main-sequence evolution of stars I. Importance of accretion efficiency and deuterium abundance

Author

Kunitomo, Masanobu, Guillot, Tristan, Takeuchi, Taku, Ida, Shigeru, Kunitomo, Masanobu, Guillot, Tristan, Takeuchi, Taku, and Ida, Shigeru

Abstract

Recent theoretical work has shown that the pre-main-sequence (PMS) evolution of stars is much more complex than previously envisioned. Instead of the traditional steady, one-dimensional solution, accretion may be episodic and not necessarily symmetrical, thereby affecting the energy deposited inside the star and its interior structure. Given this new framework, we want to understand what controls the evolution of accreting stars. We use the MESA stellar evolution code with various sets of conditions. In particular, we account for the (unknown) efficiency of accretion in burying gravitational energy into the protostar through a parameter, $\xi$, and we vary the amount of deuterium present. We confirm the findings of previous works that the evolution changes significantly with the amount of energy that is lost during accretion. We find that deuterium burning also regulates the PMS evolution. In the low-entropy accretion scenario, the evolutionary tracks in the H-R diagram are significantly different from the classical tracks and are sensitive to the deuterium content. A comparison of theoretical evolutionary tracks and observations allows us to exclude some cold accretion models ($\xi\sim 0$) with low deuterium abundances. We confirm that the luminosity spread seen in clusters can be explained by models with a somewhat inefficient injection of accretion heat. The resulting evolutionary tracks then become sensitive to the accretion heat efficiency, initial core entropy, and deuterium content. In this context, we predict that clusters with a higher D/H ratio should have less scatter in luminosity than clusters with a smaller D/H. Future work on this issue should include radiation-hydrodynamic simulations to determine the efficiency of accretion heating and further observations to investigate the deuterium content in star-forming regions. (abbrev.), Comment: Published in A&A. 16 pages, 14 figures

Published
2017
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291. Herschel special feature [editorial]

Author

Shore, S., Walmsley, C. M., Ferrara, Andrea, Guillot, Tristan Yves Nicolas, Combes, Françoise, Bertout, Claude, Jones, A., Forveille, Thierry, Shore, S., Walmsley, C. M., Ferrara, Andrea, Guillot, Tristan Yves Nicola, Combes, Françoise, Bertout, Claude, Jones, A., and Forveille, Thierry

Subjects
astrophysics, Settore FIS/05 - Astronomia e Astrofisica, Physics, Herschel, William. Astronomical theories, cosmology
Published
2010

292. Interiors of Giant Planets Inside and Outside the Solar System

Author

Guillot, Tristan

Subjects
Observations, Research, Solar System -- Observations -- Research, Planets -- Research, Solar system -- Observations -- Research
Abstract

Constraints on the interior structure of the giant planets of our solar system--Jupiter, Saturn, Uranus, and Neptune--are derived from knowledge of their mass M, equatorial radius a, and gravitational moments [...], An understanding of the structure and composition of the giant planets is rapidly evolving because of (i) high-pressure experiments with the ability to study metallic hydrogen and define the properties of its equation of state and (ii) spectroscopic and in situ measurements made by telescopes and satellites that allow an accurate determination of the chemical composition of the deep atmospheres of the giant planets. However, the total amount of heavy elements that Jupiter, Saturn, Uranus, and Neptune contain remains poorly constrained. The discovery of extrasolar giant planets with masses ranging from that of Saturn to a few times the mass of Jupiter opens up new possibilities for understanding planet composition and formation. Evolutionary models predict that gaseous extrasotar giant planets should hate a variety of atmospheric temperatures and chemical compositions, but the radii are estimated to be dose to that of Jupiter (between 0.9 and 1.7 Jupiter radii), provided that they contain mostly hydrogen and helium.

Published
1999

293. A non-grey analytical model for irradiated atmospheres⋆⋆⋆

Author

Parmentier, Vivien, Guillot, Tristan, Fortney, Jonathan J, and Marley, Mark S

Subjects
atmospheres [stars], astro-ph.SR, radiative transfer, planet-star interactions, astro-ph.EP, atmospheres [planets and satellites], Astronomy & Astrophysics, Astronomical and Space Sciences
Abstract

Context. The recent discovery and characterization of the diversity of the atmospheres of exoplanets and brown dwarfs calls for the development of fast and accurate analytical models. Aims. We wish to assess the goodness of the different approximations used to solve the radiative transfer problem in irradiated atmospheres analytically, and we aim to provide a useful tool for a fast computation of analytical temperature profiles that remains correct over a wide range of atmospheric characteristics. Methods. We quantify the accuracy of the analytical solution derived in paper I for an irradiated, non-grey atmosphere by comparing it to a state-of-the-art radiative transfer model. Then, using a grid of numerical models, we calibrate the different coefficients of our analytical model for irradiated solar-composition atmospheres of giant exoplanets and brown dwarfs. Results. We show that the so-called Eddington approximation used to solve the angular dependency of the radiation field leads to relative errors of up to ∼5% on the temperature profile. For grey or semi-grey atmospheres (i.e., when the visible and thermal opacities, respectively, can be considered independent of wavelength), we show that the presence of a convective zone has a limited effect on the radiative atmosphere above it and leads to modifications of the radiative temperature profile of approximately ∼2%. However, for realistic non-grey planetary atmospheres, the presence of a convective zone that extends to optical depths smaller than unity can lead to changes in the radiative temperature profile on the order of 20% or more. When the convective zone is located at deeper levels (such as for strongly irradiated hot Jupiters), its effect on the radiative atmosphere is again on the same order (∼2%) as in the semi-grey case. We show that the temperature inversion induced by a strong absorber in the optical, such as TiO or VO is mainly due to non-grey thermal effects reducing the ability of the upper atmosphere to cool down rather than an enhanced absorption of the stellar light as previously thought. Finally, we provide a functional form for the coefficients of our analytical model for solar-composition giant exoplanets and brown dwarfs. This leads to fully analytical pressure-temperature profiles for irradiated atmospheres with a relative accuracy better than 10% for gravities between 2.5 m s-2 and 250 m s-2 and effective temperatures between 100K and 3000 K. This is a great improvement over the commonly used Eddington boundary condition.

Published
2015

294. Antarctica Dome C astronomy activities update

Author

Moretto, Gil, Agabi, A., Aristidi, Eric, Carbillet, Marcel, Chadid, Merieme, Fossat, Eric, Guillot, Tristan, Vernin, Jean, Ziad, Aziz, Aristidi, Eric, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, and COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], [PHYS.ASTR] Physics [physics]/Astrophysics [astro-ph], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2015

295. CoRoT-2b: a Tidally Inflated, Young Exoplanet?

Author

Guillot, Tristan, Havel, Mathieu, Guillot, Tristan, Laboratoire de Cosmologie, Astrophysique Stellaire & Solaire, de Planétologie et de Mécanique des Fluides (CASSIOPEE), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, and Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.ASTR.EP] Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [PHYS.ASTR.SR] Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], [PHYS.ASTR.EP]Physics [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.SR] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astrophysics::Solar and Stellar Astrophysics, [SDU.ASTR.EP] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astrophysics::Galaxy Astrophysics
Abstract

CoRoT-2b is among the most anomalously large transiting exoplanet known. Due to its large mass (3.3 Mjup), its large radius (~1.5 Rjup) cannot be explained by standard evolution models. Recipes that work for other anomalously large exoplanets (e.g. HD209458b), such as invoking kinetic energy transport in the planetary interior or increased opacities, clearly fail for CoRoT-2b. Interestingly, the planet's parent star is an active star with a large fraction (7 to 20%) of spots and a rapid rotation (4.5 days). We first model the star's evolution to accurately constrain the planetary parameters. We find that the stellar activity has little influence on the star's evolution and inferred parameters. However, stellar evolution models point towards two kind of solutions for the star-planet system: (i) a very young system (20-40 Ma) with a star still undergoing pre-main sequence contraction, and a planet which could have a radius as low as 1.4 Rjup, or (ii) a young main-sequence star (40 to 500 Ma) with a planet that is slightly more inflated (~1.5 Rjup). In either case, planetary evolution models require a significant added internal energy to explain the inferred planet size: from a minimum of 3x1028 erg/s in case (i), to up to 1.5x1029 erg/s in case (ii). We find that evolution models consistently including planet/star tides are able to reproduce the inferred radius but only for a short period of time (~10 Ma). This points towards a young age for the star/planet system and dissipation by tides due to either circularization or synchronization of the planet. Additional observations of the star (infrared excess due to disk?) and of the planet (precise Rossiter effect, IR secondary eclispe) would be highly valuable to understand the early evolution of star-exoplanet systems.

Published
2009

296. On the filtering and processing of dust by planetesimals 1. Derivation of collision probabilities for non-drifting planetesimals

Author

Guillot, Tristan, Ida, Shigeru, Ormel, Chris W., Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Tokyo Institute of Technology [Tokyo] (TITECH), Department of Astronomy [Berkeley], University of California [Berkeley], University of California-University of California, Programme National de PlanetologieANR MOJO, and ANR-13-BS05-0003,MOJO,Modélisation du processus de croissance des planètes Joviennes/(2013)

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), Astrophysics - Solar and Stellar Astrophysics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], FOS: Physical sciences, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract

Context. Circumstellar disks are known to contain a significant mass in dust ranging from micron to centimeter size. Meteorites are evidence that individual grains of those sizes were collected and assembled into planetesimals in the young solar system. Aims. We assess the efficiency of dust collection of a swarm of non-drifting planetesimals {\rev with radii ranging from 1 to $10^3$\,km and beyond. Methods. We calculate the collision probability of dust drifting in the disk due to gas drag by planetesimal accounting for several regimes depending on the size of the planetesimal, dust, and orbital distance: the geometric, Safronov, settling, and three-body regimes. We also include a hydrodynamical regime to account for the fact that small grains tend to be carried by the gas flow around planetesimals. Results. We provide expressions for the collision probability of dust by planetesimals and for the filtering efficiency by a swarm of planetesimals. For standard turbulence conditions (i.e., a turbulence parameter $\alpha=10^{-2}$), filtering is found to be inefficient, meaning that when crossing a minimum-mass solar nebula (MMSN) belt of planetesimals extending between 0.1 AU and 35 AU most dust particles are eventually accreted by the central star rather than colliding with planetesimals. However, if the disk is weakly turbulent ($\alpha=10^{-4}$) filtering becomes efficient in two regimes: (i) when planetesimals are all smaller than about 10 km in size, in which case collisions mostly take place in the geometric regime; and (ii) when planetary embryos larger than about 1000 km in size dominate the distribution, have a scale height smaller than one tenth of the gas scale height, and dust is of millimeter size or larger in which case most collisions take place in the settling regime. These two regimes have very different properties: we find that the local filtering efficiency $x_{filter,MMSN}$ scales with $r^{-7/4}$ (where $r$ is the orbital distance) in the geometric regime, but with $r^{-1/4}$ to $r^{1/4}$ in the settling regime. This implies that the filtering of dust by small planetesimals should occur close to the central star and with a short spread in orbital distances. On the other hand, the filtering by embryos in the settling regime is expected to be more gradual and determined by the extent of the disk of embryos. Dust particles much smaller than millimeter size tend only to be captured by the smallest planetesimals because they otherwise move on gas streamlines and their collisions take place in the hydrodynamical regime. Conclusions. Our results hint at an inside-out formation of planetesimals in the infant solar system because small planetesimals in the geometrical limit can filter dust much more efficiently close to the central star. However, even a fully-formed belt of planetesimals such as the MMSN only marginally captures inward-drifting dust and this seems to imply that dust in the protosolar disk has been filtered by planetesimals even smaller than 1 km (not included in this study) or that it has been assembled into planetesimals by other mechanisms (e.g., orderly growth, capture into vortexes). Further refinement of our work concerns, among other things: a quantitative description of the transition region between the hydro and settling regimes; an assessment of the role of disk turbulence for collisions, in particular in the hydro regime; and the coupling of our model to a planetesimal formation model., Comment: Accepted for publication in A\&A. 31 pages, 29 figures. (Version corrected by the A\&A Language Editor)

Published
2014

297. In situ Probe Science at Saturn

Author

Atkinson, David, Mousis, Olivier, Lunine, Jonathan I., Simon-Miller, Amy A., Atreya, Sushil K., Brinckerhoff, W., Colaprete, A., Coustenis, Athéna, Fletcher, Leigh N., Guillot, Tristan, Lebreton, Jean-Pierre, Mahaffy, P. R., Orton, Glenn S., Reh, Kim R., Spilker, Linda J., Spilker, Thomas R., Webster, C., University of Idaho [Moscow, USA], Université de Franche-Comté (UFC), Université Bourgogne Franche-Comté [COMUE] (UBFC), Center for Radiophysics and Space Research, Cornell University (CRSR), NASA/Goddard Space Flight Center (NASA/GSFC), University of Michigan, NASA Ames Research Center (NASA Ames), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Pôle Planétologie du LESIA, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Flat Wavefronts, Observatoire de la Côte d'Azur (OCA), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), NASA Jet Propulsion Lab / California Institute of Technology, and Systems Engineering and Asssessment Ltd

Subjects
[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

International audience; A fundamental goal of solar system exploration is to understand the origin of the solar system, the initial stages, conditions, and processes by which the solar system formed, how the formation process was initiated, and the nature of the interstellar seed material from which the solar system was born. Key to understanding solar system formation and subsequent dynamical and chemical evolution is the origin and evolution of the giant planets and their atmospheres. Several theories have been put forward to explain the process of solar system formation, and the origin and evolution of the giant planets and their atmospheres. Each theory offers quantifiable predictions of the abundances of noble gases He, Ne, Ar, Kr, and Xe, and abundances of key isotopic ratios 4He/3He, D/H, 15N/14N, 18O/16O, and 13C/12C. Detection of certain disequilibrium species, diagnostic of deeper internal processes and dynamics of the atmosphere, would also help discriminate between competing theories. Measurements of the critical abundance profiles of these key constituents into the deeper well-mixed atmosphere must be complemented by measurements of the profiles of atmospheric structure and dynamics at high vertical resolution and also require in situ exploration. The atmospheres of the giant planets can also serve as laboratories to better understand the atmospheric chemistries, dynamics, processes, and climates on all planets including Earth, and offer a context and provide a ground truth for exoplanets and exoplanetary systems. Additionally, Giant planets have long been thought to play a critical role in the development of potentially habitable planetary systems. In the context of giant planet science provided by the Galileo, Juno, and Cassini missions to Jupiter and Saturn, a small, relatively shallow Saturn probe capable of measuring abundances and isotopic ratios of key atmospheric constituents, and atmospheric structure including pressures, temperatures, dynamics, and cloud locations and properties not accessible by remote sensing can serve to test competing theories of solar system and giant planet origin, chemical, and dynamical evolution.

Published
2014

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