scholarly journals Modelling extrasolar planetary atmospheres

2009 ◽  
Vol 5 (H15) ◽  
pp. 695-696
Author(s):  
France Allard
Keyword(s):  
Spectral Properties ◽  
High Spatial Resolution ◽  
Dust Cloud ◽  
Surface Wind ◽  
Giant Planets ◽  
Cloud Formation ◽  
Tidal Effects ◽  
Hydrodynamic Simulations ◽  
Stellar Radiation ◽  
Thermal Escape

AbstractThe atmospheres of close-in Extrasolar Giant Planets (EGPs) experience important stellar radiation, raising the question of the heat redistribution around the planetary surface and of the importance of photochemistry effects for their spectral properties. They experience mass loss via quasi-thermal escape of their lightest elements. They rotate and experience tidal effects. Model atmospheres struggle to include even part of this complexity. Some address the dynamics of the atmospheres as a whole (3D) as subjected to rotation, or as patches of the surface (wind studies), compromising on the details of the composition and radiative/convective properties. Others solve the composition and radiative/convective properties, compromising on dynamical effects such as rotation. In this paper, we review existing model atmospheres for EGPs, and present the first high spatial resolution local (as opposed to global) 2/3D radiation hydrodynamic simulations of EGP atmospheres including dust cloud formation.

scholarly journals A comparison of chemistry and dust cloud formation in ultracool dwarf model atmospheres

2008 ◽  
Vol 391 (4) ◽  
pp. 1854-1873 ◽  
Author(s):  
Ch. Helling ◽  
A. Ackerman ◽  
F. Allard ◽  
M. Dehn ◽  
P. Hauschildt ◽  
...  
Keyword(s):  
Dust Cloud ◽  
Cloud Formation

scholarly journals Ploonets: formation, evolution, and detectability of tidally detached exomoons

2019 ◽  
Vol 489 (2) ◽  
pp. 2313-2322 ◽  
Author(s):  
Mario Sucerquia ◽  
Jaime A Alvarado-Montes ◽  
Jorge I Zuluaga ◽  
Nicolás Cuello ◽  
Cristian Giuppone
Keyword(s):  
Planetary System ◽  
Orbital Evolution ◽  
Giant Planets ◽  
Light Curves ◽  
Significant Evidence ◽  
Object A ◽  
Tidal Interactions ◽  
Stellar Radiation ◽  
Planetary Migration ◽  
Intense Research

Abstract Close-in giant planets represent the most significant evidence of planetary migration. If large exomoons form around migrating giant planets which are more stable (e.g. those in the Solar system), what happens to these moons after migration is still under intense research. This paper explores the scenario where large regular exomoons escape after tidal interchange of angular momentum with its parent planet, becoming small planets by themselves. We name this hypothetical type of object a ploonet. By performing semi-analytical simulations of tidal interactions between a large moon with a close-in giant, and integrating numerically their orbits for several Myr, we found that in ∼50 per cent of the cases a young ploonet may survive ejection from the planetary system, or collision with its parent planet and host star, being in principle detectable. Volatile-rich ploonets are dramatically affected by stellar radiation during both planetocentric and siderocentric orbital evolution, and their radius and mass change significantly due to the sublimation of most of their material during time-scales of hundreds of Myr. We estimate the photometric signatures that ploonets may produce if they transit the star during the phase of evaporation, and compare them with noisy light curves of known objects (Kronian stars and non-periodical dips in dusty light curves). Additionally, the typical transit timing variations (TTV) induced by the interaction of a ploonet with its planet are computed. We find that present and future photometric surveys’ capabilities can detect these effects and distinguish them from those produced by other nearby planetary encounters.

scholarly journals Atmospheric Circulation of Hot Jupiters

2004 ◽  
Vol 202 ◽  
pp. 261-268 ◽  
Author(s):  
Tristan Guillot
Keyword(s):  
Large Scale ◽  
Circulation Model ◽  
Giant Planets ◽  
Large Temperature ◽  
Strong Wind ◽  
Temperature Variations ◽  
Hot Jupiters ◽  
Stellar Radiation ◽  
Synchronous Rotation ◽  
Night Side

About 40% of the extrasolar giant planets discovered so far have orbital distances smaller than 0.2 AU. These “hot Jupiters” are expected to be in synchronous rotation with their star. The ability to measure their radii prompts a careful reexamination of their structure. I show that their atmospheric structure is complex and that thermal balance cannot be achieved through radiation only but must involve heat advection by large-scale circulation. A circulation model inspired from Venus is proposed, involving a relatively strong zonal wind (with a period that can be as short as 1 day). It is shown that even this strong wind is incapable of efficiently redistributing heat from the day side to the night side. Temperature variations of 200 K or more are to be expected, even at pressures as large as 10 bar. As a consequence, clouds should be absent on the day side, allowing more efficient absorption of the stellar light. The global chemical composition of the atmosphere should also be greatly affected by the presence of large temperature variations. Finally, stellar tides may also be important in their ability to deposit heat at levels untouched by stellar radiation, thereby slowing further the cooling of the planets.

scholarly journals Consistent Simulations of Substellar Atmospheres and Nonequilibrium Dust Cloud Formation

2008 ◽  
Vol 675 (2) ◽  
pp. L105-L108 ◽  
Author(s):  
Christiane Helling ◽  
Matthias Dehn ◽  
Peter Woitke ◽  
Peter H. Hauschildt
Keyword(s):  
Dust Cloud ◽  
Cloud Formation

Analysis of the long-term surface wind variability over complex terrain using a high spatial resolution WRF simulation

2012 ◽  
Vol 40 (7-8) ◽  
pp. 1643-1656 ◽  
Author(s):  
Pedro A. Jiménez ◽  
J. Fidel González-Rouco ◽  
Juan P. Montávez ◽  
E. García-Bustamante ◽  
J. Navarro ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Complex Terrain ◽  
High Spatial Resolution ◽  
Surface Wind ◽  
Wind Variability

scholarly journals The ASKOS experiment for the validation of Aeolus L2A aerosol product 

2021 ◽  
Author(s):  
Eleni Marinou ◽  
Vasslis Amiridis ◽  
Ioanna Mavropoulou ◽  
Holger Baars ◽  
Stelios Kazadzis ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Microwave Radiometer ◽  
Dust Cloud ◽  
Cape Verde ◽  
Particle Orientation ◽  
Atmospheric Composition ◽  
Spherical Particles ◽  
Cloud Formation ◽  
In Situ Sensors

<p>For the in-orbit calibration and validation of the Aeolus products, ESA organized the Aeolus Tropical campaign, which will take place on June-July 2021 at Cape Verde region. During the campaign, Aeolus underfights will be performed with several aircrafts (by DLR, NASA, LATMOS, and the University of Nova Gorica (UNG)) and advanced ground-based instrumentation will be deployed in Mindelo island within ASKOS (https://askos.space.noa.gr/) experiment. ASKOS observations will provide an unprecedented dataset for the aerosol and wind conditions in the region, in order to provide reference values for the Cal/Val of the mission. Apart from the main aerosol Cal/Val objective of ASKOS, the foreseen synergistic activities will provide a wealth of information to address scientific questions posed by the participating groups on dust characterization, transportation and it’s impact of radiation and cloud formation.</p><p>Here, we report on the status of the ASKOS preparations for the evaluation of the aerosol and cloud product, focusing on the instrumentation requirements and availability, as well as the engagement of the scientific community so far. ASKOS will deploy advanced ground-based and airborne remote sensing and in-situ instrumentation, including the full ACTRIS aerosol and cloud remote sensing/in-situ facilities and airborne in-situ sensors to be operated on drones and/or aircrafts. The main ground-based remote sensing instrumentation in Cape Verde will consist of sophisticated lidar systems, including the EVE lidar, a circular polarization system that is tailored to mimic the Aeolus measurement from ground, the multi-wavelength Polly-XT and the WALL-E prototype for detecting particle orientation. The instrumentation will also include sun-photometers such as AERONET-CIMEL, but also polarimeters to advance microphysical retrievals for non-spherical particles such as dust. Cloud remote sensors including a cloud radar and a microwave radiometer will operate in parallel along with meteorological radiosondes. In-situ sensors at surface and onboard UAVs and light aircrafts will be available. ASKOS will be fully supported by several operational modeling simulations for meteorological and atmospheric composition forecasting. ASKOS will remain open to contributions from other communities and research groups and more synergies will be pursued in the future.</p><p> </p>

scholarly journals Giant Planets, Tiny Stars: Producing Short-period Planets around White Dwarfs with the Eccentric Kozai–Lidov Mechanism

2021 ◽  
Vol 922 (1) ◽  
pp. 4
Author(s):  
Alexander P. Stephan ◽  
Smadar Naoz ◽  
B. Scott Gaudi
Keyword(s):  
Direct Evidence ◽  
Giant Planet ◽  
Giant Planets ◽  
Tidal Effects ◽  
Stellar Envelope ◽  
Orbital Parameters ◽  
Short Period ◽  
Migration Mechanism ◽  
Red Giant ◽  
Host Stars

Abstract The recent discoveries of WD J091405.30+191412.25 (WD J0914 hereafter), a white dwarf (WD) likely accreting material from an ice-giant planet, and WD 1856+534 b (WD 1856 b hereafter), a Jupiter-sized planet transiting a WD, are the first direct evidence of giant planets orbiting WDs. However, for both systems, the observations indicate that the planets’ current orbital distances would have put them inside the stellar envelope during the red-giant phase, implying that the planets must have migrated to their current orbits after their host stars became WDs. Furthermore, WD J0914 is a very hot WD with a short cooling time that indicates a fast migration mechanism. Here, we demonstrate that the Eccentric Kozai–Lidov Mechanism, combined with stellar evolution and tidal effects, can naturally produce the observed orbital configurations, assuming that the WDs have distant stellar companions. Indeed, WD 1856 is part of a stellar triple system, being a distant companion to a stellar binary. We provide constraints for the orbital and physical characteristics for the potential stellar companion of WD J0914 and determine the initial orbital parameters of the WD 1856 system.

scholarly journals UV Absorption by Silicate Cloud Precursors in Ultra-hot Jupiter WASP-178b

2021 ◽  
Author(s):  
Joshua Lothringer ◽  
David Sing ◽  
Zafar Rustamkulov ◽  
Hannah Wakeford ◽  
Kevin Stevenson ◽  
...  
Keyword(s):  
Transmission Spectrum ◽  
Middle Atmosphere ◽  
Theoretical Models ◽  
Giant Planets ◽  
Cloud Formation ◽  
Spectral Features ◽  
Theoretical Expectation ◽  
Refractory Elements ◽  
Wavelength Absorption ◽  
Hot Jupiter

Abstract Aerosols have been found to be nearly ubiquitous in substellar atmospheres. Evidence for the composition and conditions whereby these aerosols form remains limited (Cushing et al. 2006, Saumon & Marley 2008, Burningham 2021). Theoretical models and observations of muted spectral features suggest that silicate clouds play an important role in exoplanets between at least 950 and 2,100 K (Gao et al. 2020). However, some giant planets are thought to be hot enough to avoid condensation of even the most refractory elements (Lothringer et al. 2018, Kitzmann et al. 2018). Here, we present the near-UV transmission spectrum of an ultra-hot Jupiter WASP-178b (~2,450 K), that exhibits significant NUV absorption indicating the presence of gaseous refractory elements in the middle atmosphere. This short-wavelength absorption is among the largest spectral features ever observed in an exoplanet in terms of atmospheric scale heights. Bayesian retrievals indicate the broadband UV feature on WASP-178b is caused by refractory elements including silicon and magnesium bearing species, which are the precursors to condensate clouds at lower temperatures. Silicon in particular has not been detected in exoplanets before, but the presence of SiO in WASP-178b is consistent with theoretical expectation as the dominant Si-bearing species at high temperatures. These observations allow us to re-interpret previous observations of HAT-P-41b and WASP-121b to suggest that silicate cloud formation begins on exoplanets with equilibrium temperatures between 1,950 and 2,350 K.

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