Transiting exoplanets from the CoRoT space mission: XI. CoRoT-8b: A hot and dense sub-Saturn around a K1 dwarf

P. Bordé*, F. Bouchy, M. Deleuil, J. Cabrera, L. Jorda, C. Lovis, S. Csizmadia, S. Aigrain, J. M. Almenara, R. Alonso, M. Auvergne, A. Baglin, P. Barge, W. Benz, A. S. Bonomo, H. Bruntt, L. Carone, S. Carpano, H. Deeg, R. DvorakA. Erikson, S. Ferraz-Mello, M. Fridlund, D. Gandolfi, J. C. Gazzano, M. Gillon, E. Guenther, T. Guillot, P. Guterman, A. Hatzes, M. Havel, G. Hébrard, H. Lammer, A. Léger, M. Mayor, T. Mazeh, C. Moutou, M. Pätzold, F. Pepe, M. Ollivier, D. Queloz, H. Rauer, D. Rouan, B. Samuel, A. Santerne, J. Schneider, B. Tingley, S. Udry, J. Weingrill, G. Wuchterl

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Aims. We report the discovery of CoRoT-8b, a dense small Saturn-class exoplanet that orbits a K1 dwarf in 6.2 days, and we derive its orbital parameters, mass, and radius. Methods. We analyzed two complementary data sets: the photometric transit curve of CoRoT-8b as measured by CoRoT and the radial velocity curve of CoRoT-8 as measured by the HARPS spectrometer. Results. We find that CoRoT-8b is on a circular orbit with a semi-major axis of 0.063 ± 0.001 AU. It has a radius of 0.57 ± 0.02 RJ, a mass of 0.22 ± 0.03 MJ, and therefore a mean density of 1.6 ± 0.1 g cm-3. Conclusions. With 67% of the size of Saturn and 72% of its mass, CoRoT-8b has a density comparable to that of Neptune (1.76 g cm-3). We estimate its content in heavy elements to be 47-63 M, and the mass of its hydrogen-helium envelope to be 7-23 M. At 0.063 AU, the thermal loss of hydrogen of CoRoT-8b should be no more than ∼0.1% over an assumed integrated lifetime of 3 Ga.

Original languageEnglish
Article numberA66
JournalAstronomy and Astrophysics
Issue number10
StatePublished - 2010


FundersFunder number
Science and Technology Facilities CouncilST/G002266/1
Science and Technology Facilities Council
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung130468
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung


    • planets and satellites: detection
    • planets and satellites: fundamental parameters
    • stars: fundamental parameters
    • techniques: photometric
    • techniques: radial velocities
    • techniques: spectroscopic


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