The effects of passing stellar encounters on planet formation and implications to formation of dust debris disk around main sequence stars

恒星通常以星团的形式形成。由于它们的空间密度很高，星团中的恒星之间会经历密切的碰撞，直到星团在10^8-10^9年的时间尺度上被分解。在这样的初始阶段，行星很可能正在形成并受到恒星相遇的影响。我们特别研究了这种影响，认为凯珀带天体的轨道分布显示出这种相遇的特征。通过数值计算，我们发现，一颗从太阳经过约100AU的恒星可以在40-47AU处对当前Keiper带天体的高度偏心轨道负责，并抑制30AU以上的大行星的形成，这与现在的太阳系是一致的。超过30AU，小行星的碰撞导致分裂而不是吸积，导致尘埃碎片盘的形成。类似的尘埃产生过程也将发生在太阳系外的行星系统中。观测表明，来自中心恒星的尘埃碎片盘存在于30AU以上。我们的结果与观测结果是一致的。我们已多次在美国天文学会DPS会议上发表了这些成果，并在DPS的S期刊《伊卡洛斯》上发表了两篇相关论文，并提交了另外两篇论文。

Stars are generally formed in clusters. Since their spatial density is high, stars in clusters experience close concounters with each other until the clusters are broken up on timescales of 10^8-10^9 years. In such initial stages, planets are likely to be being formed and be affected by the stellar encounters. We have investigated the effects, in particular, suggested that the orbital distribution of Keiper belt objects show signature of such encounters. Through numerical calculations, we showed that a star passing through about 100 AU from the Sun can be responsible for the highly eccentric orbits of current Keiper belt objects at 40-47 AU and inhibit formation of large planets beyond 30 AU, which is consistenet with present Solar system. Beyond 30 AU, collisions of planetesimals result in disruption rather than accretion, resulting in formation of a dust debris disk. Similar dust production processes would occur also in extrasolar planetary systems. Observations show that dust debris disks exist beyond 30 AU from central stars. Our result is consistent with the observations. We have presented these results at DPS meetings of American Astronomical Society a few times, and published two related papers in DPS' s journal "Icarus" and submitted another two papers.