Radiation Study of Two Very Bright Terrestrial Bolides and an Application to the Comet S–L 9 Collision with Jupiter
Radiation Study of Two Very Bright Terrestrial Bolides and an Application to the Comet S–L 9 Collision with Jupiter
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两个非常明亮的地球火流星的辐射研究及其在 S-L 9 彗星与木星碰撞中的应用
DOI：
10.1006/icar.1996.0104
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发表时间：
1996
期刊：
影响因子：
3.2
通讯作者：
P. Spurný
中科院分区：
文献类型：
--
作者：
J. Borovička;P. Spurný
摘要研究了两颗最亮的被拍摄到的火流星的光曲线和光谱。苏门答腊火流星的绝对星等达到了- 21.5等（即100公里距离）。这颗初始质量约为5000公斤的脆弱彗星体出现了许多耀斑，并在距地表59公里的高度消失。贝涅索夫火流星（- 19.5等）是一个初始质量约13000千克的石质天体，辐射至17千米高空，在24千米高空出现明亮的耀斑并伴有严重的碎裂。结果表明，碎裂是主要的烧蚀方式。通过对Sumava的光曲线进行建模，发现在随后的五次分裂中，大约85%的初始质量损失了。即使在破裂之间，烧蚀系数也远远高于熔化和汽化的理论值。光谱表明，这两种化合物的辐射都是由加热到4000-5000 K的气体产生的。在这个温度下，只有烧蚀的物质才会辐射；大气的辐射可以忽略不计。原子和分子辐射在大部分轨迹中占主导地位，但在最大光热连续辐射附近也存在。这些结果被推广到苏梅克-列维9号彗星进入木星大气层的情况。由于高烧蚀，预计彗星核不会穿透木星云以下。由于相关的火流星的辐射体积在光学上是厚的，火流星仍然相对暗淡，并且火流星的亮度对撞击体质量只有微弱的依赖。这一结果与伽利略号宇宙飞船对火球和火流星的观测结果一致。
Abstract Lightcurves and spectra of two of the brightest photographed bolides were studied. The Sumava bolide reached −21.5 absolute (i.e., 100 km distance) magnitude. This fragile cometary body of initial mass of about 5000 kg exhibited many flares and disappeared at an altitude of 59 km above the surface. The Benesov bolide (−19.5 mag) was a stony body of initial mass of about 13,000 kg which radiated down to 17 km of altitude and exhibited a bright flare at 24 km accompanied with severe fragmentation. It is shown that the fragmentation was the main mode of ablation. By modeling the lightcurve of Sumava it is found that about 85% of the initial mass was lost in five subsequent breakups. Even between the breakups, the ablation coefficient is found to be much higher than the theoretical value for melting and vaporization. The spectra show that the radiation of both bolides was produced by a gas heated to 4000–5000 K. At this temperature only the ablated material radiates; the radiation of the atmosphere was negligible. Atomic and molecular emissions are dominant for most of the trajectory, but near the maximum light thermal continuous radiation is also present. The results were generalized for the entry of the comet Shoemaker–Levy 9 into the Jupiter atmosphere. Due to the high ablation, the cometary nuclei are not expected to penetrate below the jovian clouds. As the radiating volume of the associated bolides is optically thick, the bolides remain relatively faint and only weak dependence of the bolide brightness on the impactor mass is produced. The results are in accordance with the bolide and fireball observations from the Galileo spacecraft.