Tidal Processes in Planetary and Stellar Systems

地球上每天都有潮汐，它们在天体领域也广泛发生。在这里，我建议研究它们的两种表现形式。* * * * * *热木星。第一批已知的太阳系外行星，以令人难以置信的近距离围绕它们的恒星运行。它们经常被认为是动态迁移的产物：形成时距离它们现在的位置远得多，与它们的邻居（恒星或行星）的角动量交换可能会逐渐将它们原来的圆形轨道压缩成非常狭窄的椭圆；当这些行星周期性地在恒星周围摇摆时，会产生强烈的潮汐。如果潮汐晃动能够消散为热量，行星轨道就会衰减，热木星就诞生了。这种动态迁移理论，虽然很好地解释了热木星的许多观察到的特征，但也包含了一些主要的弱点——所有这些都与我们对潮汐过程缺乏理解有关。所以为了牢固地确立热木星的起源，我建议对潮汐过程进行详细的研究。在这样的研究结束时，我们应该能够解释这些行星当前的轨道和大小。最终理解大自然创造的这类奇异的物体将是令人满意的。******另一个非常极端的潮汐过程发生在当一颗小行星非常接近一个大质量物体（行星或恒星）的表面时。前者的身体可以被粉碎成数百万个小碎片，其中一些碎片逃脱了毁灭者的引力，最终重新聚集成更大的团块。我们提出，这样的灾难性事件可能是我们在恒星周围看到的许多明亮的尘埃盘，即所谓的碎片盘的产生原因。这与传统的碎片盘形成理论不同，传统的理论认为，大量的星子在早期无法与行星结合，在数十亿年的时间里，它们留在了行星后面，逐渐磨碎成尘埃。我建议研究潮汐破坏事件的细节，以便预测这可能引起的碎片盘的频率和外观。这样的工作也适用于我们太阳系的柯伊伯带天体。

Tides are experienced daily here on Earth, they also occur widely in the celestial realm. Here, I propose to study two of their manifestations.******Hot Jupiters. the first-known population of extra-solar planets, orbit their stars at implausibly close ranges. They are often suggested to be the products of dynamical migration: formed much further away than their current locations, angular momentum exchange with their neighbours (either stellar or planetary ones) may gradually squeeze their original round orbits into very narrow ellipses; strong tides are raised on these planets as they sway by their stars periodically. If the tidal sloshing can be dissipated into heat, the planet orbit will decay and a hot Jupiter is born. Such a theory of dynamical migration, while neatly explaining many of the observed features of hot Jupiters, contains a number of major weaknesses -- all related to our lack of understandings on the tidal process. So in order to firmly establish the origin of hot Jupiters, I propose to study the tidal process in detail. At the end of such a study, we should be able to explain the current orbits and sizes of these planets. It will be satisfying to finally understand this class of exotic objects that nature produces.******Another very extreme tidal process occurs when a small planet passes very close from the surface of a massive body (a planet or a star). The former body can be shredded into millions of little debris, with some of them escaping the gravitational pull of the destroyer and eventually re-conglomerating into larger clumps. Such a catastrophic event, we propose, may be responsible for producing the many bright dusty disks we see around stars, the so-called debris disks. This breaks away from the conventional picture of debris disk formation, where it is hypothesized that quantities of planetesimals, unable to be incorporated into planets at early days, remain behind and gradually grind down to dust over billions of years. I propose to study the details of the tidal disruption event, in order to predict the frequency and the appearance of debris disks this can give rise to. Such a work also have applications for the Kuiper belt objects in our own solar system.