Transiting exoplanets from the CoRoT space mission. XX. CoRoT-20b: A very high density, high eccentricity transiting giant planet

LUTH, Observatoire de Paris, CNRS, Université Paris Diderot, 5 place Jules Janssen, 92195, Meudon, France
Astronomy and Astrophysics (Impact Factor: 4.38). 01/2012; 538:145. DOI: 10.1051/0004-6361/201117681
Source: arXiv


We report the discovery by the CoRoT space mission of a new giant
planet, CoRoT-20b. The planet has a mass of 4.24 ± 0.23
MJup and a radius of 0.84 ± 0.04 RJup. With
a mean density of 8.87 ± 1.10 g cm-3, it is among the
most compact planets known so far. Evolutionary models for the planet
suggest a mass of heavy elements of the order of 800 M⊕
if embedded in a central core, requiring a revision either of the planet
formation models or both planet evolution and structure models. We note
however that smaller amounts of heavy elements are expected by more
realistic models in which they are mixed throughout the envelope. The
planet orbits a G-type star with an orbital period of 9.24 days and an
eccentricity of 0.56.The star's projected rotational velocity is vsini =
4.5 ± 1.0 km s-1, corresponding to a spin period of
11.5 ± 3.1 days if its axis of rotation is perpendicular to the
orbital plane. In the framework of Darwinian theories and neglecting
stellar magnetic breaking, we calculate the tidal evolution of the
system and show that CoRoT-20b is presently one of the very few
Darwin-stable planets that is evolving toward a triple synchronous state
with equality of the orbital, planetary and stellar spin periods.

The CoRoT space mission, launched on December 27th 2006, has been
developed and is operated by CNES, with the contribution of Austria,
Belgium, Brazil, ESA (RSSD and Science Programme), Germany, and Spain.

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