标题： 甲烷行星及其质量和半径的关系 显示英文标题

标题： Methane Planets and their Mass-Radius Relation

摘要： 已知系外行星的质量和半径，我们可以估算其平均密度以及由此推测其组成。 系外行星在质量和组成方面似乎占据了非常大的参数空间，与太阳系中的行星不同，系外行星还具有中间质量（~ 5 - 50 M_Earth）且具有各种密度。 在这封信中，我们研究了甲烷 (CH_4) 行星的质量-半径关系的行为，并表明当甲烷行星足够大（Mp >~ 15 M_Earth）时，甲烷可以解离，导致分化行星，该行星具有碳核心、甲烷包层和氢大气层。 还考虑了岩石核心对 CH_4 行星行为的贡献。 我们还为几个可能为甲烷/富含甲烷的中间质量行星开发了内部模型。 甲烷行星的例子强调了质量-半径关系的复杂性以及唯一推断行星组成的挑战。 显示英文摘要

摘要： Knowledge of both the mass and radius of an exoplanet allows us to estimate its mean density, and therefore its composition. Exoplanets seem to fill a very large parameter space in terms of mass and composition, and unlike the solar-system's planets, exoplanets also have intermediate masses (~ 5 - 50 M_Earth) with various densities. In this letter, we investigate the behavior of the Mass-Radius relation for methane (CH_4) planets and show that when methane planets are massive enough (Mp >~ 15 M_Earth), the methane can dissociate and lead to a differentiated planet with a carbon core, a methane envelope, and a hydrogen atmosphere. The contribution of a rocky core to the behavior of CH_4 planet is considered as well. We also develop interior models for several detected intermediate-mass planets that could, in principle, be methane/methane-rich planets. The example of methane planets emphasizes the complexity of the Mass-Radius relation and the challenge involved in uniquely inferring the planetary composition.