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Making A Meteor
Moffett Field CA (SPX) Jun 20, 2005 NASA's Deep Impact mission is about to smash into comet 9P/Tempel 1 to excavate a crater and probe the comet's internal structure. It's possible, however, that the comet will break into fragments, creating a cloud of meteoroids. That, say astronomers, may not be unnatural. "If comet 9P/Tempel 1 breaks during NASA's Deep Impact mission on July 4, a meteoroid stream will be created in much the same manner as the mechanism that causes most of our meteor showers," according to SETI Institute astronomer Dr. Peter Jenniskens in a paper accepted for publication in the Astronomical Journal. Jenniskens has discovered a fragment of lost comet D/1819 W1 (Blanpain), last seen in 1819. It has survived for 36 orbits, and was detected on November 22, 2003 by the Catalina Sky Survey as a minor planet called 2003 WY25. It passed Earth at a distance of only 0.025 AU (3.7 million kilometers) on December 11, 2003. After its orbit was better determined, Jenniskens traced the object back to that of Blanpain in 1819. 2003 WY25 is a tiny object, only 400 meters in diameter, assuming that, like similar objects, it reflects about 4% of the sunlight that hits it. Jenniskens and co-author Esko Lyytinen, an amateur astronomer from Finland, calculated how the debris of a breakup in 1819 would have spread under the influence of planetary perturbations. They discovered that a breakup during (or just before) the return of 1819 can explain a spectacular shower of meteors that radiated from the constellation of Phoenix in 1956. In that year, the planet Jupiter had steered the trail of debris into Earth's path.
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