A super-Earth transiting a nearby low-mass star

David Charbonneau, Zachory K. Berta, Jonathan Irwin, Christopher J. Burke, Philip Nutzman, Lars A. Buchhave, Christophe Lovis, Xavier Bonfils, David W. Latham, Stéphane Udry, Ruth A. Murray-Clay, Matthew J. Holman, Emilio E. Falco, Joshua N. Winn, Didier Queloz, Francesco Pepe, Michel Mayor, Xavier Delfosse, Thierry Forveille

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538 Scopus citations

Abstract

A decade ago, the detection of the first transiting extrasolar planet provided a direct constraint on its composition and opened the door to spectroscopic investigations of extrasolar planetary atmospheres. Because such characterization studies are feasible only for transiting systems that are both nearby and for which the planet-to-star radius ratio is relatively large, nearby small stars have been surveyed intensively. Doppler studies and microlensing have uncovered a population of planets with minimum masses of 1.9-10 times the Earths mass (M ), called super-Earths. The first constraint on the bulk composition of this novel class of planets was afforded by CoRoT-7b (refs 8, 9), but the distance and size of its star preclude atmospheric studies in the foreseeable future. Here we report observations of the transiting planet GJ 1214b, which has a mass of 6.55M and a radius 2.68 times Earths radius (R ), indicating that it is intermediate in stature between Earth and the ice giants of the Solar System. We find that the planetary mass and radius are consistent with a composition of primarily water enshrouded by a hydrogen-helium envelope that is only 0.05% of the mass of the planet. The atmosphere is probably escaping hydrodynamically, indicating that it has undergone significant evolution during its history. The star is small and only 13 parsecs away, so the planetary atmosphere is amenable to study with current observatories.

Original languageEnglish (US)
Pages (from-to)891-894
Number of pages4
JournalNature
Volume462
Issue number7275
DOIs
StatePublished - Dec 17 2009

All Science Journal Classification (ASJC) codes

  • General

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    Charbonneau, D., Berta, Z. K., Irwin, J., Burke, C. J., Nutzman, P., Buchhave, L. A., Lovis, C., Bonfils, X., Latham, D. W., Udry, S., Murray-Clay, R. A., Holman, M. J., Falco, E. E., Winn, J. N., Queloz, D., Pepe, F., Mayor, M., Delfosse, X., & Forveille, T. (2009). A super-Earth transiting a nearby low-mass star. Nature, 462(7275), 891-894. https://doi.org/10.1038/nature08679