Architecture of Planetary Systems: Solar and Extrasolar

行星系统的结构：太阳系和太阳系外

• 批准号: 1109776
• 负责人: Yoram Lithwick
• 金额: $ 39.84万
• 依托单位: Northwestern University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-01 至 2015-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1109776&HistoricalAwards=false
• 关键词: Architecture; Planetary; Systems; Solar; Extrasolar

If one were to arbitrarily put multiple planets in orbit around a star, one might find the system to be dynamically unstable: the orbits would deviate exponentially from their original paths on time scales of a few orbital periods. Real planetary systems, which have survived for at least millions of orbits, are not dynamically unstable. On these long time scales, a planet behaves as if its mass were spread around its orbit, like an elliptical ring around the star. These rings pull on each other gravitationally, causing slow changes in their shapes and orientations, which may lead to so-called secular instability or secular chaos. The Principal Investigator and collaborators on this project plan to develop a complete theory of secular instability, using analytic techniques as well as computer simulations of interacting elliptical rings and direct N-body simulations. Their goal is to determine whether secular instability and secular chaos can quantitatively explain and predict (1) the long-term orbital evolution of the Inner Planets, (2) the distribution of orbital properties and masses of "hot Jupiter" exoplanets, and (3) the properties of exoplanet systems in general. In particular, they aim to determine whether secular chaos is a viable alternative to disk-driven migration for the formation of hot Jupiters which may be able also to account for the wide distribution of orbital inclinations with respect to the stellar equator. They will make quantitative predictions for the eccentricities and spacings of extrasolar planets, and build an understanding of how observations of exoplanet systems can be used to constrain planet formation physics. The project will support and train one postdoctoral researcher and two undergraduate summer students, and the Principal Investigator will give public presentations on the results of the work.

如果人们任意地将多颗行星置于围绕一颗恒星的轨道上，人们可能会发现该系统在动态上不稳定：在几个轨道周期的时间尺度上，轨道会以指数方式偏离其原始路径。真实的行星系统至少已经存在了数百万个轨道，在动态上并不是不稳定的。在这些长的时间尺度上，行星的行为就好像其质量分布在其轨道上，就像围绕恒星的椭圆环一样。这些环在引力作用下相互吸引，导致其形状和方向缓慢变化，这可能导致所谓的长期不稳定或长期混乱。该项目的首席研究员和合作者计划使用分析技术以及相互作用椭圆环的计算机模拟和直接 N 体模拟来开发一套完整的长期不稳定性理论。他们的目标是确定长期不稳定和长期混沌是否可以定量解释和预测（1）内行星的长期轨道演化，（2）“热木星”系外行星的轨道特性和质量的分布，以及（3）系外行星系统的一般特性。特别是，他们的目标是确定长期混沌是否是盘驱动迁移的可行替代方案，以形成热木星，这也可能能够解释相对于恒星赤道的轨道倾角的广泛分布。他们将对太阳系外行星的偏心率和间距进行定量预测，并了解如何利用系外行星系统的观测来约束行星形成物理学。该项目将支持和培训一名博士后研究员和两名本科暑期学生，首席研究员将就工作成果进行公开演讲。