METEORS BY MOONLIGHT
Armagh Observatory, 7 August 2000:
On the night of Friday 11th/Saturday 12th August, the annual meteor shower known as the Perseids makes its return. The meteors may be seen at any time during the hours of darkness, but it is usually best to view them after midnight when the observer is travelling head-on into the stream of particles that cause the shower.
The Perseids are caused by debris from Comet Swift-Tuttle streaking at very high speeds through the Earth's atmosphere. Most of the particles making up the debris are no larger than a grain of sand, but some pieces may be the size of a pebble, causing a bright fireball.
The constellation Perseus, the area from which the meteors appear to radiate, will be low in the northeast. Allow your eyes about 15 minutes to become adapted to the dark. The Moon will be approaching its full phase, hampering the detection of faint meteors, but from 40 to 60 shooting stars per hour may be seen at a dark observing site during the peak of activity.
As Mark Littmann, author of "The Heavens on Fire," recounts, an American bookstore owner, Edward Herrick, independently discovered the Perseids on 9th August, 1837. He later made a thorough search of astronomical records and found several references to sightings of meteors on 9th and 10th August from Egypt in 1029 to England in 1833. Herrick commented that a meteor shower at this time of year has been known for a long time.
Littmann further comments that the meteors are sometimes referred to as the Tears of St. Lawrence, who was martyred on 10th August, 258. There was a belief among early German folk that Lawrence wept tears of fire which fell from the sky every year on his anniversary.
FOR FURTHER INFORMATION CONTACT John McFarland at the Armagh Observatory, tel.: 028-3752-2928.
See also: The Perseid Stream
Last Revised: 10th August 2000
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