Debris disks in extrasolar planetary systems

目前已知有超过220颗附近的恒星在它们的轨道上有太阳系外行星。也有相当数量的恒星被小行星和彗星碎片带所包围。现在有一种新出现的恒星，像我们的太阳一样，在它们的系统中既有行星，也有碎片。通过研究这些精选的“行星碎片”恒星，我们将能够帮助弄清楚行星系统是如何形成和演化的。这个项目将要研究的一种“行星-碎片”系统是在其行星系统的内部受到异常大量碎片的轰击时被发现的。我们可能在一个类似于太阳系“晚期重轰炸”时期的时代见证这些系统，一个50兆尔的事件被认为发生在3.8千兆尔以前，在此期间，地球和月球遭受了异常大量的彗星涌入。在另一种类型的“行星-碎片”系统中，一颗（或多颗）类木星行星的轨道比碎片离母星更近，但它们影响的证据可能仍然印在碎片带的结构上。这种结构可以用来确定行星系统的历史，并为尚未见过的绕恒星运行的行星提供证据。这个项目旨在通过观测和理论建模的结合来研究这些行星系统。所获得的关于这些系统的信息，更广泛地说，关于决定太阳系外行星系统的最终结构和这些系统的后续演化的物理过程的信息，将有助于回答人类提出的一些最持久的哲学问题。这些问题包括我们的太阳系有多独特，以及像我们的地球这样能够维持生命的行星有多常见。

Over 220 nearby stars are now known to have extrasolar planets in orbit around them. A comparable number of stars are also known to be surrounded by belts of asteroidal and cometary debris. There is now an emerging population of stars that, like our own Sun, have both planets and debris in their systems. By studying this select bunch of 'planet-debris' stars we will be able to help work out how planetary systems form and evolve. One type of 'planet-debris' system this project will study is being seen at a time when the inner reaches of its planetary system are being bombarded by an unusually high quantity of debris. We may be witnessing these systems at an epoch akin to the period of 'Late Heavy Bombardment' in the solar system, a 50Myr event thought to have happened 3.8Gyr ago during which the Earth and Moon were subjected to an unusually large influx of comets. In another type of 'planet-debris' system, one (or more) Jupiter-like planets orbit much closer to the parent star than the debris, yet evidence for their influence may still be imprinted on the structure of the debris belt. That structure can be used to ascertain the history of the planetary system and provide evidence for as yet unseen planets orbiting the star. This project aims to study these planetary systems through a mixture of both observations and theoretical modelling. The information gained about these systems, and more generally about the physical processes which determine the final architecture of extrasolar planetary systems and the subsequent evolution of those systems, will help to answer some of the most enduring philosophical questions that mankind has posed. These include questions about how unique our solar system is, and how common planets are that, like our own Earth, are capable of sustaining life.