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GEMINID METEORS

Armagh Observatory, 10 December 2001:
Maximum activity of the annual Geminid meteor shower will occur around 04.00 on the morning of Friday 14 December. This meteor shower, which reaches a peak of up to 120 meteors per hour, as seen from a clear, dark site, can be observed anytime after about 10.00pm for a few nights either side of the maximum, that is from about the 12 to 16 December.

The Geminid meteors, which sometimes appear as brightly coloured relatively slow-moving fireballs, are caused by small particles mostly about the size of marbles or smaller, ejected into space from the surface of the near-Earth asteroid Phaethon. They are extremely unusual, because most meteors appear to come from comets. Astronomers still do not understand how this asteroid came to be the source of such a rich meteoroid stream, the two main ideas being that Phaethon had a catastrophic collision hundreds of years ago with another minor planet, which ejected masses of dust into space, or that Phaethon itself was once a more active object, losing material every revolution on its 17-month orbit around the Sun, in the same way as a comet.

Geminid meteors have been seen every year since they were first noticed in 1862. However, their source remained a mystery for many years until the discovery of the asteroid Phaethon in 1983 and detective work by the astronomer Fred L. Whipple that finally made the connection. Owing to Phaethon's asteroidal orbit, the meteoroids run into the Earth's atmosphere at the relatively slow speed of about 80,000 miles per hour, leading to the typically long, slow trails of the brighter fireballs.

In order to observe Geminid meteors, select a clear, dark sky after about 10.00pm, with a good view towards the North, East or South. The meteors appear to radiate from a point near the star Castor, in the constellation of Gemini, which is high in the eastern sky at 10.00pm. Wrap up warm, and allow 10 minutes for your eyes to become accustomed to the dark. Then, weather permitting, you should see Geminids.

The sky over Armagh at 4.00am Friday 14th December 2001.
From the Heavens Above web site.

There are several other interesting objects visible at this time, including the very bright planet Jupiter (close to the Geminid radiant) and the slightly less bright Saturn, to the upper right of the constellation Orion, a little above the bright red star Aldebaran in Taurus.

The International Space Station will also be visible as a slowly moving, star-like object on, and a few days either side of, 13th December, generally travelling from the south-west towards the south or south-east. For Northern Ireland viewers times are as follows: 11 Dec., 5:27 p.m. and 7:02 p.m.; 12 Dec., 7:36 p.m.; 13 Dec., 4:59 p.m. and 6: 35 p.m.; 14 Dec., 5:33 p.m. and 7:09 p.m. It is advisable to start watching for the space station a few minutes before these times.

See also:
Geminids 2003
Gary Kronk's Site
NASA Site
(3200) Phaethon

FOR FURTHER INFORMATION CONTACT John McFarland at the Armagh Observatory, tel.: 028-3752-2928, e-mail: jmf@star.arm.ac.uk.

Last Revised: 2003 December 2nd
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