象限仪座流星雨母体被发现
SETI研究所的天文学家Peter Jenniskens认为，象限仪座流星雨的母体是编号为2003 EH1的小天体。Dead comet spawned New Year meteors
Astronomers may have pinpointed source of the Quadrantids.
31 December 2003
PHILIP BALL
Keep your eyes on the heavens at the turn of the year, say astronomers - you might spot streaking Quadrantids.
The meteor shower has lit up the early January skies since at least 1825. Now astronomer Peter Jenniskens of the SETI Institute in Mountain View, California, may have tracked down the source of the shooting stars.
The Quadrantids could be debris from a celestial body called 2003 EH1, Jenniskens says. 2003 EH1, which was discovered in March, was previously thought to be an asteroid on an orbit that brings it close to Earth.
Jennisken believes that 2003 EH1 may in fact be a washed-up comet1. It broke up about 500 years ago, he suggests, releasing a scattering of dusty grains that hit Earth's atmosphere and burn up to create the Quadrantids' light-show.
Most other meteor showers, such as the November Leonids, are also sparked when Earth periodically passes through a comet's dusty debris. The dust trail is replenished each time it returns to the inner solar system, and so the annual meteor showers become more spectacular.
Light show
The Quadrantids, which are generally rather faint, seem to emanate from the constellation of Boötes, close to the Big Dipper. The best view is obtained in the Northern Hemisphere from about 11 pm GMT. The show is typically at its most spectacular around 2-4 January.
Astronomers have long known that these meteors originated from some 'parent body', but were unable to agree on what it was. By looking at the meteor trajectories, Jenniskens calculated the orbit that this parent body would now be following and found that it closely fits the path of 2003 EH1.
Astronomers suspect that 2003 EH1 may itself be the remnant of a larger parent comet called C1490 Y1. In 1979, Japanese astronomer Ishiro Hasegawa discovered that the path of the Quadrantids seemed to be similar to that of C1490 Y1, which is mentioned in East Asian historical records from around 1490 and broke up roughly a century later.
Jenniskens teamed up with Brian Marsden of the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, to see whether they could match the predicted orbit of EH1 to that of C1490 Y1 at around the time that it broke up. This is tricky, because the orbits of C1490 Y1 and 2003 EH1 could have been shifted by close flybys of Earth or Jupiter.
The researchers conclude that 2003 EH1 might be the ancient core of C1490 Y1 - but the evidence is scant. They need better observations of the path currently followed by 2003 EH1. But if the once-obscure 2003 EH1 does turn out to be the heart of an extinct comet, it would make an enticing target for future space missions.
References
Jenniskens, P. 2003 EH1 is the Quadrantid shower parent comet. Astronomical Journal, Preprint, See also International Astronomical Union circular 8252, 8 December 2003. (2003).
© Nature News Service / Macmillan Magazines Ltd 2003
顶！
这个流星群的神秘程度不亚于天龙座流星雨。。。希望母体的发现能够对今后的预报工作产生积极的推动作用::070821_06.jpg::
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