All told, comet hunter Donald Machholz of Colfax, California, has had a banner year. In July he codiscovered a 9.5-magnitude visitor in Camelopardalis. The following month he swept up a new, 10th-magnitude periodic comet, which happened to be fractured in six pieces. Then on October 8th he discovered yet another, a 12th-magnitude interloper in Ursa Major. This latest catch brings to nine Machholz's total number of visual discoveries. He thus replaces David H. Levy of Tucson, Arizona, as the most prolific living comet discoverer in the Western Hemisphere. Currently leading Machholz are Australian amateur William Bradfield with 16 visual discoveries and Czech astronomer Antonin Mrkos with 11. For the remainder of this year Comet Machholz, 1994r, will travel southwest through the evening sky, traversing Lynx, Auriga, Taurus, and Cetus.
Meanwhile, Periodic Comet Machholz 2 has lost some of the predawn luster it had in past weeks. According to SKY & TELESCOPE columnist John Bortle, the main fragment, A, is still fairly obvious but has faded to magnitude 9.9. Fragment D is fainter still, at 11.2, but Bortle says a Lumicon Swan-band filter enhances its visibility. However, this week the Moon will be moving into the morning sky, making the comet a tough target no matter what.
Clearly better, says Bortle, is Periodic Comet Borrelly. He says it's very prominent even though its estimated magnitude is 8.9 That's because the coma is 2'.6 across and markedly condensed. There's even a distinct jet seen to jutting eastward. Borrelly has begun to cross the winter Milky Way, and you'll find it in the late-night sky about halfway between the bright stars Procyon and Betelgeuse. Here are positions for 0 hours Universal time:
R.A. Dec.
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Oct. 15 6h 56m + 6.1 deg
Oct. 17 7 1 + 7.0
Oct. 19 7 6 + 7.9
NASA's Magellan orbiter ended its tremendously successful mission to Venus with a dive toward the cratered surface it first revealed. The spacecraft fell silent at 3:02 a.m. Wednesday, October 12, about a day after flight controllers at the Jet Propulsion Laboratory commanded it to fire thrusters and plunge deeply into the upper atmosphere of Venus. Magellan was expected to flutter down to the surface, possibly in several pieces, about 1 p.m. Thursday. Magellan has been orbiting Venus for five years, providing spectacular radar images of that cloudy world and, more recently, providing a sensitive probe of the planet's gravity.
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