Bourrier, Vincent; Lovis, Christophe; Beust, Hervé; Ehrenreich, David; Henry, Gregory W.; Astudillo-Defru, Nicola; Allart, Romain; Bonfils, Xavier; Ségransan, Damien; Delfosse, Xavier; Cegla, Heather M.; Wyttenbach, Aurélien; Lavie, Baptiste; Pepe, Francesco; Heng, Kevin (2018). Orbital misalignment of the Neptune-mass exoplanet GJ 436b with the spin of its cool star. Nature, 553(7689), pp. 477-480. Macmillan Journals Ltd. 10.1038/nature24677
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Heng_Orbital misalignment of the Neptune-mass exoplanet GJ 436b with the spin of its cool star.pdf - Accepted Version Available under License Publisher holds Copyright. Download (6MB) | Preview |
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nature24677.pdf - Published Version Restricted to registered users only Available under License Publisher holds Copyright. Download (2MB) |
The angle between the spin of a star and its planets' orbital planes traces the history of the planetary system. Exoplanets orbiting close to cool stars are expected to be on circular, aligned orbits because of strong tidal interactions with the stellar convective envelope. Spin-orbit alignment can be measured when the planet transits its star, but such ground-based spectroscopic measurements are challenging for cool, slowly-rotating stars. Here we report the characterization of a planet three-dimensional trajectory around an M dwarf star, derived by mapping the spectrum of the stellar photosphere along the chord transited by the planet. We find that the eccentric orbit of the Neptune-mass exoplanet GJ 436b is nearly perpendicular to the stellar equator. Both eccentricity and misalignment, surprising around a cool star, can result from dynamical interactions (via Kozai migration) with a yet-undetected outer companion. This inward migration of GJ 436b could have triggered the atmospheric escape that now sustains its giant exosphere. Eccentric, misaligned exoplanets orbiting close to cool stars might thus hint at the presence of unseen perturbers and illustrate the diversity of orbital architectures seen in exoplanetary systems.
Item Type: |
Journal Article (Original Article) |
|---|---|
Division/Institute: |
08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences 08 Faculty of Science > Physics Institute 10 Strategic Research Centers > Center for Space and Habitability (CSH) 08 Faculty of Science > Physics Institute > NCCR PlanetS |
UniBE Contributor: |
Heng, Kevin |
Subjects: |
500 Science 500 Science > 520 Astronomy 500 Science > 530 Physics |
ISSN: |
0028-0836 |
Publisher: |
Macmillan Journals Ltd. |
Language: |
English |
Submitter: |
Janine Jungo |
Date Deposited: |
18 Apr 2018 14:11 |
Last Modified: |
05 Dec 2022 15:11 |
Publisher DOI: |
10.1038/nature24677 |
BORIS DOI: |
10.7892/boris.112375 |
URI: |
https://boris.unibe.ch/id/eprint/112375 |
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