关于太阳系外行星的宜居性
On the Habitability of Extra-Solar Planets
中文摘要：
愈来愈多的太阳系外行星的发现激发了人们对发现太阳系外生命的热情期待。在诸多决定生命存在的因素中，液态水的存在是一个关键性的因素。因此，确定一颗太阳系外行星是否宜居，其首要条件是该行星的表面温度是否能够保证液态水的长期存在。简要介绍位于红矮星宜居带内的行星的宜居性研究进展。由于潮汐锁相作用，该类行星的一面永远面对恒星，较为温暖；而另一面永远背对恒星，极端寒冷。极低的温度有可能导致大气成分和水分完全冻结在背阳
面，并导致行星不适宜生命存在。在此，讨论大气和海洋环流能否输送足够多的热量到背阳面，并加热背阳面，从而避免大气和水分的完全冻结。最后，根据地球大气和海洋环流以及热量输送的知识对这些问题加以阐述。
面，并导致行星不适宜生命存在。在此，讨论大气和海洋环流能否输送足够多的热量到背阳面，并加热背阳面，从而避免大气和水分的完全冻结。最后，根据地球大气和海洋环流以及热量输送的知识对这些问题加以阐述。
中文关键词：
太阳系外行星，宜居性，大气海洋热量输送，行星气候
KeyWords：
exoplanets, habitability, atmospheric and oceanic heat transport, planetary climate
Abstract：
Discoveries of more and more extra-solar planets (exoplanets) stimulate our great enthusiasm in searching for extrasolar life in deep space. Among many factors that life requires, permanent existence of liquid water is considered the most critical one. Thus, the first criterion in determining the habitability of an exoplanet is whether its surface temperature guarantees the existence of liquid water, which is a problem of climate. The present paper will briefly introduce the progress of research of the habitability of exoplanets in the habitable zone of M dwarfs. Exoplanets in the habitable zone around M dwarfs are very likely tidally-locked planets due to strong gravitational forces, because they are so close to their M dwarfs. That is, such exoplanets are in the synchronous rotating state, with which one side of these exoplanets permanently faces their primaries and is warm, while the other side remains dark and cold. If the nightside temperature is sufficiently low, atmosphere compositions and water would be all frozen over the nightside, and such tidal-locking exoplanets are uninhabitable. Here, we will address the question, with our knowledge of Earth’s climate system, whether the atmosphere and ocean are able to transport sufficient heat from the dayside to the nightside to prevent atmosphere from collapse and water from being frozen on the nightside, or not.