Rabinowitz D, Helin E, Lawrence K, Pravdo S
Yale University Physics Department, New Haven, Connecticut 06511, USA.
Nature. 2000 Jan 13;403(6766):165-6. doi: 10.1038/35003128.
Near-Earth asteroids are small (diameters < 10 km), rocky bodies with orbits that approach that of the Earth (they come within 1.3 AU of the Sun). Most have a chance of approximately 0.5% of colliding with the Earth in the next million years. The total number of such bodies with diameters > 1 km has been estimated to be in the range 1,000-2,000, which translates to an approximately 1% chance of a catastrophic collision with the Earth in the next millennium. These numbers are, however, poorly constrained because of the limitations of previous searches using photographic plates. (One kilometre is below the size of a body whose impact on the Earth would produce global effects.) Here we report an analysis of our survey for near-Earth asteroids that uses improved detection technologies. We find that the total number of asteroids with diameters > 1 km is about half the earlier estimates. At the current rate of discovery of near-Earth asteroids, 90% will probably have been detected within the next 20 years.
近地小行星是小型（直径<10千米）的岩石天体，其轨道接近地球轨道（它们到太阳的距离在1.3天文单位以内）。大多数近地小行星在未来100万年与地球碰撞的概率约为0.5%。据估计，直径大于1千米的此类天体总数在1000至2000个之间，这意味着在下个千年中，与地球发生灾难性碰撞的概率约为1%。然而，由于此前使用照相底片进行搜索存在局限性，这些数字的准确性较差。（1千米小于对地球产生全球影响的天体大小。）在此，我们报告一项利用改进探测技术对近地小行星进行的调查分析。我们发现，直径大于1千米的小行星总数约为早期估计值的一半。按照目前发现近地小行星的速度，90%的近地小行星可能会在未来20年内被发现。
