系外行星的形状与其内部结构

发布时间：2018-10-17 07:39

【摘要】：随着观测技术不断进步,已经有了很多对系外行星扁率和拱点进动的观测进展.行星的扁率是由行星的内部密度剖面与其自转决定的,勒夫数k_2与其核的大小存在明显的负相关.故扁率与k_2可以很好地限定系外行星的内部结构.从Lane-Emden方程出发,构建了不同多方指数下的行星模型.继而通过解算Wavre的积分微分方程得到其扁率,结果表明:多方指数越小,自转越快,扁率越大.从NASA(美国国家航空航天局)系外行星表中,挑选了469个同时具有质量、半径和轨道周期观测或估算值的系外行星,在两种不同自转周期假设下,计算了它们的扁率.结果表明:如果采用潮汐锁定假设,绝大多数系外行星的扁率非常小,约97%的行星小于0.01,难以被观测到;而在固定的10.55 h自转周期假设下,有28%的行星扁率大于0.1.通过解算Zharkov简化的2阶微分方程,得到了不同多方模型下的勒夫数,并讨论了k_2与核大小的关系.
[Abstract]:With the development of observational technology, there has been much progress in observing the oblateness of exoplanets and the precession of arch points. The flattening of a planet is determined by the inner density profile of the planet and its rotation, and there is a significant negative correlation between the Lefer number KS _ 2 and the size of its nucleus. Therefore, flatness and Ks _ 2 can well define the internal structure of exoplanets. Based on the Lane-Emden equation, the planetary models with different multiparty exponents are constructed. Then the flat ratio of Wavre is obtained by solving the integro-differential equation of Wavre. The results show that the smaller the multiparty index, the faster the rotation and the larger the flat ratio. From the NASA (National Aeronautics and Space Administration) list of exoplanets, 469 exoplanets with mass, radius and orbital period observations or estimates were selected and their flattening was calculated under two different rotation cycle assumptions. The results show that the flat ratio of most exoplanets is very small, about 97% of the planets are less than 0.01, which is difficult to be observed, and 28% of the planets with fixed rotation period of 10.55 h are more than 0.1 under the assumption of tidal locking. By solving the 2-order differential equation simplified by Zharkov, the Lefer numbers in different multiparty models are obtained, and the relation between KS _ 2 and kernel size is discussed.
【作者单位】：中国科学院上海天文台;中国科学院行星科学重点实验室;
【基金】：国家自然科学基金项目(11373058、10903023、11133004) 中国科学院行星科学重点实验室开放课题资助
【分类号】：P15

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