Comet Shoemaker‐Levy 9 Fragment Size Estimates: How Big Was the Parent Body? a
Comet Shoemaker‐Levy 9 Fragment Size Estimates: How Big Was the Parent Body? a
复制标题
Shoemaker-Levy 9 彗星碎片大小估计：母体有多大？
DOI：
10.1111/j.1749-6632.1997.tb48340.x
复制
发表时间：
1995
影响因子：
5.2
通讯作者：
D. Crawford
中科院分区：
文献类型：
--
作者：
D. Crawford
摘要：1994年7月，舒梅克-列维9号彗星撞击木星，这是有史以来规模最大、能量最强的行星撞击事件。由于它在1992年与木星近距离接触时解体，因此它足够明亮，在撞击前一年多就被发现，这使科学界有了前所未有的机会来评估这种事件的影响。许多优秀的观测是从地球上的望远镜，哈勃太空望远镜（HST）和伽利略航天器前往木星。在本文中，这些观测结果与CTH冲击物理学水代码进行的计算模拟相结合，以确定在行星上形成可辨别的撞击特征的15个碎片的大小。为此，CTH配备了辐射烧蚀模型和后处理辐射射线跟踪能力，可以为伽利略和地面观测者的观测几何结构进行光通量预测（通常称为撞击闪光）。对伽利略号记录的五次事件进行了校准，以估计碎片的大小。与地面和HST观测结果相比，这些估计值使用最小二乘分析进行了扩展，以评估其余10个碎片的影响。一些最大的撞击（L、G和K）直径大于1公里，但碎片密度很低，约为0.25克/立方厘米。15个碎片的体积加在一起将形成一个直径为1.8公里的球体。假设分裂前的密度为0.5 g/cm 3，那么舒梅克-列维9号的母体可能直径为1.4 km。所有撞击的总动能相当于300千兆吨TNT的爆炸当量。
ABSTRACT: The impact of Comet Shoemaker‐Levy 9 on Jupiter in July, 1994 was the largest, most energetic impact event on a planet ever witnessed. Because it broke up during a close encounter with Jupiter in 1992, it was bright enough to be discovered more than a year prior to impact, allowing the scientific community an unprecedented opportunity to assess the effects such an event would have. Many excellent observations were made from Earth‐based telescopes, the Hubble Space Telescope (HST), and the Galileo spacecraft en route to Jupiter. In this paper, these observations are used in conjunction with computational simulations performed with the CTH shock‐physics hydrocode to determine the sizes of the fifteen fragments that made discernible impact features on the planet. To do this, CTH was equipped with a radiative ablation model and a postprocessing radiative ray‐trace capability that enabled light‐flux predictions (often called the impact flash) for the viewing geometries of Galileo and ground‐based observers. The five events recorded by Galileo were calibrated to give fragment size estimates. Compared against ground‐based and HST observations, these estimates were extended using a least‐squares analysis to assess the impacts of the remaining ten fragments. Some of the largest impacts (L, G, and K) were greater that 1 km in diameter, but the density of the fragments was low, about 0.25 g/cm3. The volume of the combined fifteen fragments would make a sphere 1.8 km in diameter. Assuming a prebreakup density of 0.5 g/cm3, the parent body of Shoemaker‐Levy 9 had a probable diameter of 1.4 km. The total kinetic energy of all the impacts was equivalent to the explosive yield of 300 Gigatons of TNT.