Meteors Perseids

Fig. 5. Photograph taken by Millman showing the spectrum of a fast meteor (Perseid, average velocity of 59 km/s, altitude = 100 km). Note the presence of metallic ions in addition to metallic neutrals, as well as a more complex atmospheric spectrum. This photograph is shown by permission of the University of Chicago Press and is taken from a paper by Millman. ...

Many attempts have been made to obtain spectra of meteor trails. Probably the best spectra ever obtained were by Millman and his colleagues at the Dominion Observatory. Figures 4 and 5 are a comparison of spectra stemming from a slow (probably Giacobinid) and a fast (Perseid) meteor, respectively. The spectrum of the low velocity meteor exhibits neutral emission lines of Mg, Fe, and Ca, the most abundant metals in most meteoroids. The strong Na D lines as well as a hint at excited N2 are also visible. By contrast, the spectrum of the high velocity meteor shows very... 

Probably the best known meteor shower is the one known as the Perseid shower. This shower reaches its peak on the night of August 12th each year, but meteors can be observed from the stream for several weeks on either side of the maximum. The shower s radiant first appears in the constellation of Andromedia in mid-July, and by late August it has moved into the constellation of Camelopardalis. The radiant is in the constellation of Perseus on the night of the shower maximum. 

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. 

If the comet s path crosses Earth s path, then at that point meteor showers are observable as the Earth passes through the trail of debris. The Perseid meteor shower occurs every year between August 9 and 13 when the Earth passes through the orbit of the comet Swift-Tuttle. Halley s comet is the source of the Orionid shower in October. 

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