Atmospheric characterization of cold exoplanets using a 1.5-m coronagraphic space telescope
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...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | en_US |
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EDP Sciences
2013
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| Online Access: | http://hdl.handle.net/1721.1/80774 https://orcid.org/0000-0002-7791-5124 |
| _version_ | 1826196403826720768 |
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| author | Maire, Anne-Lise Galicher, Raphael Boccaletti, Anthony Baudoz, Pierre Schneider, J. Cahoy, Kerri Stam, D. M. Traub, W. A. |
| author2 | Massachusetts Institute of Technology. Department of Aeronautics and Astronautics |
| author_facet | Massachusetts Institute of Technology. Department of Aeronautics and Astronautics Maire, Anne-Lise Galicher, Raphael Boccaletti, Anthony Baudoz, Pierre Schneider, J. Cahoy, Kerri Stam, D. M. Traub, W. A. |
| author_sort | Maire, Anne-Lise |
| collection | MIT |
| description | 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 10-8−10-10 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.
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.
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.
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. |
| first_indexed | 2024-09-23T10:26:18Z |
| format | Article |
| id | mit-1721.1/80774 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T10:26:18Z |
| publishDate | 2013 |
| publisher | EDP Sciences |
| record_format | dspace |
| spelling | mit-1721.1/807742022-09-30T21:07:07Z Atmospheric characterization of cold exoplanets using a 1.5-m coronagraphic space telescope Maire, Anne-Lise Galicher, Raphael Boccaletti, Anthony Baudoz, Pierre Schneider, J. Cahoy, Kerri Stam, D. M. Traub, W. A. Massachusetts Institute of Technology. Department of Aeronautics and Astronautics Cahoy, Kerri 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 10-8−10-10 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. 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. 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. 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. France. Ministère de l'éducation nationale (Doctoral fellowship) 2013-09-17T16:16:30Z 2013-09-17T16:16:30Z 2012-05 2012-02 Article http://purl.org/eprint/type/JournalArticle 0004-6361 1432-0746 http://hdl.handle.net/1721.1/80774 Maire, A.-L., R. Galicher, A. Boccaletti, P. Baudoz, J. Schneider, K. L. Cahoy, D. M. Stam, and W. A. Traub. “Atmospheric characterization of cold exoplanets using a 1.5-m coronagraphic space telescope.” Astronomy & Astrophysics 541 (May 3, 2012): A83. https://orcid.org/0000-0002-7791-5124 en_US http://dx.doi.org/10.1051/0004-6361/201218954 Astronomy & Astrophysics Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf EDP Sciences EDP Sciences |
| spellingShingle | Maire, Anne-Lise Galicher, Raphael Boccaletti, Anthony Baudoz, Pierre Schneider, J. Cahoy, Kerri Stam, D. M. Traub, W. A. Atmospheric characterization of cold exoplanets using a 1.5-m coronagraphic space telescope |
| title | Atmospheric characterization of cold exoplanets using a 1.5-m coronagraphic space telescope |
| title_full | Atmospheric characterization of cold exoplanets using a 1.5-m coronagraphic space telescope |
| title_fullStr | Atmospheric characterization of cold exoplanets using a 1.5-m coronagraphic space telescope |
| title_full_unstemmed | Atmospheric characterization of cold exoplanets using a 1.5-m coronagraphic space telescope |
| title_short | Atmospheric characterization of cold exoplanets using a 1.5-m coronagraphic space telescope |
| title_sort | atmospheric characterization of cold exoplanets using a 1 5 m coronagraphic space telescope |
| url | http://hdl.handle.net/1721.1/80774 https://orcid.org/0000-0002-7791-5124 |
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