planetary systems; methods: numerical; techniques: high angular resolution; techniques: image processing; techniques: imaging spectroscopy; Astrophysics - Instrumentation and Methods for Astrophysics; Astrophysics - Earth and Planetary Astrophysics
Abstract :
[en] Context. High-contrast imaging is currently the only available technique for the study of the thermodynamical and compositional properties of exoplanets in long-period orbits, comparable to the range from Venus to Jupiter. The SPICES (Spectro-Polarimetric Imaging and Characterization of Exoplanetary Systems) project is a coronagraphic space telescope dedicated to the spectro-polarimetric analysis of gaseous and icy giant planets as well as super-Earths at visible wavelengths. So far, studies for high-contrast imaging instruments have mainly focused on technical feasibility because of the challenging planet/star flux ratio of 10[SUP]-8[/SUP]-10[SUP]-10[/SUP] required at short separations (200 mas or so) to image cold exoplanets. However, the main interest of such instruments, namely the analysis of planet atmospheric/surface properties, has remained largely unexplored. <BR /> Aims: The aim of this paper is to determine which planetary properties SPICES or an equivalent direct imaging mission can measure, considering realistic reflected planet spectra and instrument limitation. <BR /> Methods: We use numerical simulations of the SPICES instrument concept and theoretical planet spectra to carry out this performance study. We also define a criterion on the signal-to-noise ratio of the measured spectrum to determine under which conditions SPICES can retrieve planetary physical properties. <BR /> Results: We find that the characterization of the main planetary properties (identification of molecules, effect of metallicity, presence of clouds and type of surfaces) would require a median signal-to-noise ratio of at least 30. In the case of a solar-type star ≤10 pc, SPICES will be able to study Jupiters and Neptunes up to ~5 and ~2 AU respectively, because of the drastic flux decrease with separation. It would also analyze cloud and surface coverage of super- Earths of radius 2.5 Earth radii at 1 AU. Finally, we determine the potential targets in terms of planet separation, radius and distance for several stellar types. For a Sun analog, we show that SPICES could characterize Jupiters (M ≥ 30 Earth masses) as small as 0.5 Jupiter radii at ≲2 AU up to 10 pc, and super-Earths at 1-2 AU for the handful of stars that exist within 4-5 pc. Potentially, SPICES could perform analysis of a hypothetical Earth-size planet around α Cen A and B. However, these results depend on the planetary spectra we use, which are derived for a few planet parameters assuming a solar-type host star. Grids of model spectra are needed for a further performance analysis. Our results obtained for SPICES are also applicable to other small (1-2 m) coronagraphic space telescopes.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Maire, Anne-Lise ; LESIA, Observatoire de Paris, CNRS, University Pierre et Marie Curie Paris 6 and University Denis Diderot Paris 7, 5 place Jules Janssen, 92195, Meudon, France ; Groupement d'Intérêt Scientifique Partenariat Haute Résolution Angulaire Sol Espace (PHASE) between ONERA, Observatoire de Paris, IPAG, LAM, CNRS and University Denis Diderot Paris 7, France
Galicher, R.; National Research Council Canada, Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, BC, V9E 2E7, Canada ; Dépt. de Physique, Université de Montréal, C.P. 6128, Succ. Centre-Ville, Montréal, QC, H3C 3J7, Canada
Boccaletti, A.; LESIA, Observatoire de Paris, CNRS, University Pierre et Marie Curie Paris 6 and University Denis Diderot Paris 7, 5 place Jules Janssen, 92195, Meudon, France ; Groupement d'Intérêt Scientifique Partenariat Haute Résolution Angulaire Sol Espace (PHASE) between ONERA, Observatoire de Paris, IPAG, LAM, CNRS and University Denis Diderot Paris 7, France
Baudoz, P.; LESIA, Observatoire de Paris, CNRS, University Pierre et Marie Curie Paris 6 and University Denis Diderot Paris 7, 5 place Jules Janssen, 92195, Meudon, France ; Groupement d'Intérêt Scientifique Partenariat Haute Résolution Angulaire Sol Espace (PHASE) between ONERA, Observatoire de Paris, IPAG, LAM, CNRS and University Denis Diderot Paris 7, France
Schneider, J.; LUTh, Observatoire de Paris, CNRS and University Denis Diderot Paris 7, 5 place Jules Janssen, 92195, Meudon, France
Cahoy, K. L.; Dept. of Aeronautics and Astronautics, MIT, 77 Mass. Ave. 37-367, Cambridge, MA, 02139, USA
Stam, D. M.; SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA, Utrecht, The Netherlands
Traub, W. A.; JPL, California Institute of Technology, M/S 301-355, 4800 Oak Grove Drive, Pasadena, CA, 91109, USA)
Language :
English
Title :
Atmospheric characterization of cold exoplanets using a 1.5-m coronagraphic space telescope
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