Tides and Atmospheres for Hot Jupiters

目前，至少有40颗太阳系外行星围绕着主序星运行，它们的周期都小于10天，最小质量小于10个木星质量。这些“热木星”的发现颠覆了之前基于太阳系的经验。它们详细的轨道和物理特性呈现出几个特殊的谜团，这些谜团可能是它们的起源、内部结构和早期原恒星环境的线索。为什么它们的平均质量明显小于那些周期较长的行星？为什么月经高峰在3天左右？为什么它们的轨道不那么偏心？假设它们是在更大的轨道上形成并向内迁移的，为什么热木星没有一直迁移到它们的恒星中，或者我们只看到了更大的初始人口的幸运幸存者？“热海王星”曾经是遭受严重质量损失的热木星吗？在为数不多的通过凌日而确定半径的热木星中，为什么这些半径比直接模型预测的要大或小得多呢？很可能许多解决方案涉及行星和恒星之间的潮汐或辐射相互作用，因为这些影响在很大程度上取决于轨道距离。杰里米·古德曼博士的研究小组将根据过去在潮汐和天体物理流体动力学中的其他问题方面的经验，调查潮汐耗散、辐射和质量损失之间的相互关系，特别关注热木星的外层。这些工具将是半分析估计和一维计算，而不是多维模拟。潮汐耗散是理论天文学中最古老的未解决问题之一。由于热木星的表面重力低，不能燃烧氢，从结构上看，它比恒星对潮汐耗散更敏感，可能更好地保留了过去潮汐影响的“记忆”。因此，对这些天体的研究可能会产生适用于更普遍的潮汐相互作用的见解。此外，公众和专业天文学家对太阳系外行星都很感兴趣，因为它们可能会教给我们太阳系的历史，甚至可能是地球以外存在生命的可能性。＊＊＊

AST 0707373GoodmanAt this time, there are at least forty extrasolar planets orbiting main-sequence stars with well-determined periods of less than 10 days and minimum masses less than 10 Jupiter masses. The discovery of these "hot Jupiters" defied previous experience based on the Solar System. Their detailed orbital and physical properties present several specific mysteries, which are probablyclues to their origins, internal structure, and early protostellar environment. Why are their masses significantly smaller on average than those of planets with longer periods? Why do the periods peak at ~3 days? Why are their orbits less eccentric? Presuming that they formed on larger orbits and migrated inward, why did the hot Jupiters not migrate all the way into their stars, or do we see only the lucky survivors of a much larger initial population? Were "hot Neptunes" once hot Jupiters that suffered severe mass loss? Among the few hot Jupiters that have well-determined radii by virtue of transiting their stars, why are many of these radii significantly larger or smaller than straightforwardmodels predict? It is likely that many of the solutions involve tidal or radiative interactionsbetween the planet and its star, as these influences depend strongly on orbital distance. Building upon past experience with tides and other problems in astrophysical fluid dynamics, Dr. Jeremy Goodman's research team will investigate the interrelations between tidal dissipation, irradiation, and mass loss, with particular attention to the outer layers of hot Jupiters. The tools will be semianalytic estimates and one dimensional calculations rather than multidimensional simulations. Tidal dissipation is among the oldest unsolved problems in theoretical astronomy. Because of their low surface gravity and inability to burn hydrogen, hot Jupiters are structurally more sensitive to tidal dissipation than stars and may better preserve a "memory" of past tidal influences. So thestudy of these objects may yield insights applicable to tidal interactions more generally. Besides, extrasolar planets are of great interest to the public as well as to professional astronomers because of the lessons they may have to teach about the history of our own solar system, and perhaps even the possibilities for life beyond earth. ***