Leonid meteor shower

Radar measurements of the Leonid meteor shower have measured entry velocities of order 70 kms-1. Routinely, the Earth passes through the debris left in space by periodic comets to produce beautiful meteor showers such as the Leonid (Figure 6.1), with observation rates as high as 100 meteors per hour. 

Figure 6.1 Leonid meteor shower. A composite of images taken by the Midcourse Space experiment satellite while in orbit around Earth. The satellite s perspective continuously changed relative to the path of the meteors, which caused their trajectories to be non-parallel. (Reproduced by permission of Jenniskens P., Nugent D., Tedesco E. and Murthy J. 2000 1997 Leonid shower from space, Earth, Moon and Planets 82/83 305)...

The radiant applies to meteors of a particular meteor stream, and is the point in infinity in the sky from which the meteors appear to come. In the case of the Leonid meteor shower that occurs annually in mid November (see Table 1), the radiant coincides with the constellation, Leo. 

Any careful study of the skies reveals the existence of meteors. It is no surprise, then, that records of meteors are among the earliest astronomical records. Apparently the oldest written account of a meteor shower is a Chinese document dating to 654 b.c.e. Some of the more spectacular meteor showers, those that reappear on a regular basis, have also been recorded and commented on for centuries. The first record of the famous Perseid meteor shower, which now occurs annually in early August, dates to a Chinese document written in 36 c.e., while Chinese astronomers made the first report of the Leonid meteor shower (now occurring each year in mid-November) in 902 c.e. 

Another meteor shower known as the Leonid occurs every year in November, caused by the tail of comet Tempel-Tuttle, which passes through the inner solar system every 32-33 years. Such a year was 1998 on November 17 and 18, 1998, observers on Earth saw as many as 200 meteors an hour. The shower was so intense that it generated widespread concern about the dismp-tion of global telecommunications and the possible damage or destmction of space telescopes. Partly as a result of careful preparation by satellite and telescope engineers, however, concerns afpeared to be minimal. 

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