Department of Astronomy, 249-17, California Institute of Technology, Pasadena, California 91125, USA.
Nature. 2009 Dec 17;462(7275):895-7. doi: 10.1038/nature08608.
The Kuiper belt is a remnant of the primordial Solar System. Measurements of its size distribution constrain its accretion and collisional history, and the importance of material strength of Kuiper belt objects. Small, sub-kilometre-sized, Kuiper belt objects elude direct detection, but the signature of their occultations of background stars should be detectable. Observations at both optical and X-ray wavelengths claim to have detected such occultations, but their implied abundances are inconsistent with each other and far exceed theoretical expectations. Here we report an analysis of archival data that reveals an occultation by a body with an approximately 500-metre radius at a distance of 45 astronomical units. The probability of this event arising from random statistical fluctuations within our data set is about two per cent. Our survey yields a surface density of Kuiper belt objects with radii exceeding 250 metres of 2.1(-1.7)(+4.8) x 10(7) deg(-2), ruling out inferred surface densities from previous claimed detections by more than 5sigma. The detection of only one event reveals a deficit of sub-kilometre-sized Kuiper belt objects compared to a population extrapolated from objects with radii exceeding 50 kilometres. This implies that sub-kilometre-sized objects are undergoing collisional erosion, just like debris disks observed around other stars.
柯伊伯带是原始太阳系的残余物。对其大小分布的测量约束了其吸积和碰撞历史，以及柯伊伯带物体材料强度的重要性。小的、亚公里大小的柯伊伯带物体难以直接探测，但它们对背景恒星的掩食的特征应该是可探测的。在光学和 X 射线波长的观测都声称已经探测到了这样的掩食，但它们所暗示的丰度彼此不一致，并且远远超过了理论预期。在这里，我们报告了对档案数据的分析，该分析揭示了一个距离为 45 个天文单位的半径约为 500 米的天体的掩食。这种事件在我们的数据集中随机统计波动中出现的概率约为 2%。我们的调查得出的结果是，半径超过 250 米的柯伊伯带物体的表面密度为 2.1(-1.7)(+4.8) x 10(7) deg(-2)，这排除了以前声称的探测结果所推断的表面密度超过 5sigma。仅检测到一个事件表明，与从半径超过 50 公里的物体推断出的种群相比，亚公里大小的柯伊伯带物体存在不足。这意味着亚公里大小的物体正在经历碰撞侵蚀，就像在其他恒星周围观测到的碎片盘一样。
