Extrasolar planets atmospheres

Using the Hubble telescope, the extrasolar planet HD 209458b (a gas planet with 0.7 times the mass of Jupiter) has been shown to have an extensive external atmosphere consisting of atomic hydrogen it is possible that the hydrogen is escaping from the planet (Vidal-Madjar et al., 2003). 

The detection of small extrasolar planets (of around the size of the Earth) will be done by registering the infrared light which they emit. Interference filters will blot out the light emitted by the star in question. Because of the huge distance from the Earth, effects due to its atmosphere and its IR radiation will not interfere. Darwin is intended not only to discover planets but to analyse their atmospheres for possible signs of life. 

Lellouch E (2011) The composition of planetary atmospheres an historical perspective. In Beaulieu J-P, Dieters S, Tinetti G (eds) Molecules in the atmospheres of extrasolar planets, ASP conference series, Paris, vol 450, pp 3-18... 

The electric dipole moments are important prerequisites for theoretical prediction of the molecular spectra as well as of the opacities and chemical abundance data. The latter are crucial ingredients for modelling atmospheres of ultracool dwarf and extrasolar planets. This review is an attempt to present an extensive picture of the existing DMSs of dipole moments for small polyatomic molecule, including those likely to be important for modelling atmospheres of such astrophysical bodies. It was also the aim of... 

The detection of atmospheres on extrasolar planet is a very difficult task. 71% of the Earth is covered by oceans but up to now it is the only planet with water in liquid form on its surface. Venus might have had water on its early history, on Mars water may exist in a frozen state near the surface and climatic changes have occurred and formed river-like structures that are observed on its surface. There exists the possibility to find condensed water in the atmospheres of Jupiter and Saturn and in deeper layers of Uranus and Neptune. Subsurface oceans may exist on several satellites of the giant planets. But how can we detect water on extrasolar planets, how can we detect whether these objects have even an atmosphere ... 

For the detection of extrasolar planetary atmospheres we are at the moment in a state similar to that 200 years ago when the first attempts were made to study atmospheres of planets in our solar system. Generally, the effects of planetary atmospheres are ... 

The detection and observation of extrasolar planets will be one of the key projects in astrophysics in the next decades. Several instruments will be available to observe the faint signatures of planets and to study by spectroscopy their atmosphere and to detect water therein. 

Brown, T.M. Transmission spectra as diagnostics of extrasolar giant planet atmospheres. Astrophys. J. 553, 1006-1026 (2001)... 

HZ is defined as the orbital area around a star where a planet can sustain liquid water at the surface. Several studies have attempted to define the HZ as a function of stellar type (e.g. F, G, K, M dwarf stars) and time (see e.g. 46, 47, and references therein). The HZ is of interest because it is widely believed that liquid water is necessary for the genesis of (recognizable) life. The particular emphasis of the planned space missions is to search for signs of life on extrasolar Earth-like planets via spectroscopy. Atmospheric compounds such as O2, O3, N2O, CH4, and CH3CI are considered biomarkers, and their spectroscopic detection in a terrestrial-type atmosphere, particularly O2 or O3 found together with a reduced gas such as CH4, would suggest life (48, 49). Detection of CO2 would indicate that the planet is indeed a terrestrial-type planet... 

Liang M-C, Seager S, Parkinson C, Lee AY-L, Yung YL (2004) On the insignificance of photochemictil hydrocarbon aerosols in the atmospheres of close-in extrasolar giant planets. Astrophys J Lett 605 L61-L64... 

Extrasolar giant planets that are close to their parent star should exhibit a complex circulation pattern. The large spatial scales of moving circulation structures on HD 209458 b may generate detectable variability of the planet s atmospheric signatures (Menou et al., 2003 [229]). 

Atmospheres of extraterrestrial planets can be directly studied during a transit. Two transit events with the Near Infrared Camera and Multi Object Spectrograph (NIC-MOS) camera on the Hubble Space Telescope (HST) were observed for the object GJ 436 b. In order to detect the atmosphere, high-cadence time series of prism spectra covering the 1.1-1.9 pm spectral range were analyzed (Pont et al., 2009 [266]). This object is an extrasolar hot Neptune. The authors measured a flat transmission spectrum at the level of a few parts per 10000 in flux, with no significant signal in the 1.4 pm water band. 

Hueso, R., Sanchez-Lavega, A. A three-dimensional model of moist convection for the giant planets II Saturn s water and ammonia moist convective storms. Icarus 172,255-271 (2004) Hui, L., Seager, S. Atmospheric lensing and oblateness effects during an extrasolar planetary transit. Astrophys. J. 572, 540-555 (2002)... 

Now, since the first extrasolar planetary systems have been detected, the search for water on such objects has just started. Because from observations it is very difficult to measure the spectroscopic signatures of the atmospheres of such planets, we have to wait for the newly planned observational facilities (both in space and on ground) some of them will be in operation very soon. 

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