太阳系外行星系统轨道参数的统计研究

自1995年第一颗类太阳恒星周围的系外行星发现以来,随着已发现的系外行星数目的增多,对系外行星性质的统计分析变得重要和有意义。截至2011年6月9日,共发现系外行星555颗。以这些系外行星的轨道参数为依据,对系外行星的性质进行统计分析,得出了一些有意义的结论。同时简要介绍现有的行星形成与演化模型并依据得出的行星统计性质对其进行检验,这对于系外行星的进一步探测具有一定的指导作用。

A Statistical Survey of Orbital Parameters of Extra-Solar Planets System

Since the first extra-solar planet around a Sun-like star was detected in 1995,the number of known extra-solar planets has been growing,which makes statistical surveys of characteristics of extra-solar planets and their host stars very important.By February 18 of 2011,527 planets had been discovered.In this paper,major techniques used for detections of extra-solar planets are introduced. Based on the physical and orbital parameters of these extra-solar planets,a statistical analysis has been carried out to investigate their properties,obtaining a number of meaningful conclusions. （1） The minimum mass of planets ranges from 0 to 25 M_Jup,with a peak around 1 M_Jup.There are very few planets beyond 12 M_Jup. （2） A bimodality is shown in the period of extra-solar planets with peaks at 3 days and 300 days and a "flat" distribution in between. （3） There are very few large-mass planets beyond 0.03 AU and the proportion of largemass planets become larger as the orbital semi-major axis increases. （4） The orbital semi-major axis and planet mass are two key factors that affect the orbital eccentricity of the planet.The orbital eccentricity decreases as the orbital semimajor axis and planet mass decreases. （5） For F-G-K stars,planets tend to be detected around metal-rich stars.When the star is more massive than the Sun,the mass of its planet is in direct proportion to the star’s mass. （6） We have discussed the properties of low-mass(M<20 M_?) planets and found that their orbital eccentricities are lower than 0.4. In this paper,we briefly introduce current models of planet formation and evolution and test the models with the derived statistical properties of planets.It therefore provides a reference for future detections of extra-solar planets.