Kenyon Scott J, Bromley Benjamin C
Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, Massachusetts 02138, USA.
Nature. 2004 Dec 2;432(7017):598-602. doi: 10.1038/nature03136.
The Kuiper belt extends from the orbit of Neptune at 30 au to an abrupt outer edge about 50 au from the Sun. Beyond the edge is a sparse population of objects with large orbital eccentricities. Neptune shapes the dynamics of most Kuiper belt objects, but the recently discovered planet 2003 VB12 (Sedna) has an eccentric orbit with a perihelion distance of 70 au, far beyond Neptune's gravitational influence. Although influences from passing stars could have created the Kuiper belt's outer edge and could have scattered objects into large, eccentric orbits, no model currently explains the properties of Sedna. Here we show that a passing star probably scattered Sedna from the Kuiper belt into its observed orbit. The likelihood that a planet at 60-80 au can be scattered into Sedna's orbit is about 50 per cent; this estimate depends critically on the geometry of the fly-by. Even more interesting is the approximately 10 per cent chance that Sedna was captured from the outer disk of the passing star. Most captures have very high inclination orbits; detection of such objects would confirm the presence of extrasolar planets in our own Solar System.
柯伊伯带从海王星轨道（距离太阳30天文单位）延伸至距太阳约50天文单位处的一个陡然的外缘。在该边缘之外是一群轨道偏心率很大的稀疏天体。海王星塑造了大多数柯伊伯带天体的动力学，但最近发现的行星2003 VB12（赛德娜）具有一个偏心率很大的轨道，其近日点距离为70天文单位，远远超出了海王星的引力影响范围。尽管路过恒星的影响可能造就了柯伊伯带的外缘，并可能将天体散射到偏心率很大的大轨道中，但目前尚无模型能够解释赛德娜的特性。在此我们表明，一颗路过恒星可能将赛德娜从柯伊伯带散射到了其观测到的轨道。一颗位于60 - 80天文单位处的行星被散射到赛德娜轨道的可能性约为50%；这一估计在很大程度上取决于近距离飞越的几何形状。更有意思的是，赛德娜有大约10%的可能性是从路过恒星的外盘被捕获的。大多数捕获的天体具有很高倾角的轨道；对这类天体的探测将证实我们太阳系中存在太阳系外行星。
