Observations of a very bright fireball and its likely link with comet C/1919 Q2 Metcalf
Observations of a very bright fireball and its likely link with comet C/1919 Q2 Metcalf
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对非常明亮的火球的观测及其可能与彗星 C/1919 Q2 梅特卡夫的联系
DOI：
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发表时间：
2009
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影响因子：
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通讯作者：
M. Jelínek
中科院分区：
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作者：
J. Trigo;J. Madiedo;I. Williams;A. Castro‐Tirado;J. Llorca;S. Vítek;M. Jelínek
2008年7月11日21:17:39 UTC，在西班牙的大部分地区以及葡萄牙和法国的部分地区观测到一个非常明亮的火球，称为B´（SPMN110708），最大亮度为- 18。幸运的是，它飞过了西班牙流星和火球网络的许多仪器，以便对其性质进行精确测量。我们描述这些观察结果，并从中推断出产生这个火球的物体的性质和起源。这颗流星在98.3公里的高度首次可见，在26公里的高度达到最大亮度，在21.5公里的高度结束。这些数值与其他众所周知的产生陨石的火球非常一致。根据流星体在大气中生存能力的标准计算表明，残存的流星体在这种高度存活下来的强度约为14兆帕，与陨星坠落的火流星相似。到目前为止，这个火球看起来很典型，人们很可能期望在适当的时候在地面上找到陨石。从观测中确定的流星体的日心轨道有一个近日点，基本上在地球轨道上，离心率为0.775，因此轨道远远超出木星，几乎达到土星的日心距离，是木星彗星家族成员的典型轨道。这与其他明亮的火球不同，远日点在小行星带内，清楚地指向小行星的起源。它的轨道也非常类似于欧米克龙龙流星雨的平均轨道，这是一个额外的指示，表明这个火球是彗星起源的。如果母体确实是一颗彗星，这就意味着彗星的内部结构一定存在着相当大的非冰内含物。这并不令人惊讶，但这可能是第一次发现直接证据表明情况确实如此。此外，这样的大块物质只能通过原子核的灾难性分裂来释放。值得注意的是，欧米克隆龙座流星雨的母体可能是彗星C/1919 Q2（梅特卡夫），这颗彗星在上个世纪的前几十年遭受了灾难性的分裂。
A very bright fireball called B´ (SPMN110708), with a maximum brightness of −18, was observed over much of Spain as well as parts of Portugal and France on 2008 July 11 at 21:17:39 UTC. Fortuitously, it flew over many of the instruments that are part of the Spanish Meteor and Fireball Network so that accurate measurements of its properties were recorded. We describe these observations and make deductions from them regarding the nature and origin of the body that gave rise to this fireball. The bolide first became visible at a height of 98.3 km, attained its maximum brightness at a height of 26 km and finished at a height of 21.5 km. These values are very much in line with other well-known fireballs producing meteorites. Standard calculations based on the meteoroids’ ability to survive in the atmosphere suggest a strength for the remnant that survived to this height of about 14 MPa, similar to those for meteorite-dropping bolides. So far, this fireball looks typical and one might well expect to find meteorites on the ground in due course. The heliocentric orbit of the meteoroid determined from the observations had a perihelion essentially at the Earth’s orbit and an eccentricity of 0.775, so that the orbit extends far beyond Jupiter, nearly reaching Saturn’s heliocentric distance and is a typical orbit for a member of the Jupiter family of comets. This is unlike other bright fireballs, where aphelion is within the asteroidal belt and clearly points to an asteroidal origin. The orbit is also very similar to the mean orbit of the Omicron Draconid meteor shower, which is an additional pointer to this fireball being of cometary origin. If the parent was indeed a comet, this has implications for the internal structure of comets in that significant-sized non-icy inclusions must exist there. This is not surprising, but this is probably the first time that direct evidence has been found showing that this is the case. Further, such chunks can only be released through the catastrophic breakup of the nucleus. Remarkably, a candidate for the parent of the Omicron Draconid meteor shower is comet C/1919 Q2 (Metcalf) which suffered a catastrophic breakup in the early decades of the last century.