dipper@utastro.UUCP (Debbie Byrd) (08/17/85)
Halley is the most famous comet. But other comets are just as interesting. More on Schwassmann-Wachmann 1 -- after this. August 17 Schwassmann-Wachmann 1 Comet Halley has been invisible this summer in the glare of the sun. But now it's becoming visible again in the predawn sky -- if you look for it with a fairly large telescope. Halley is the most famous comet. But dozens of comets return to Earth's vicinity each year -- almost all seen through telescopes only. Most come within range of our telescopes when they're closest to the sun in their very elliptical orbits. These orbits can carry them relatively near the sun -- then back to the outer solar system -- or even beyond. One interesting comet, though, has a more nearly circular orbit. It takes about 15 years to travel once around the sun -- and stays in between the orbits of the planets Jupiter and Saturn. Schwassmann-Wachmann 1 is named for two astronomers, who discovered it earlier in this century. It's interesting not only for its relatively round orbit -- but also for its large size. Its nucleus, or core, is thought to be about thirty miles across -- ten times as big as the nucleus of Comet Halley. Also, Schwassmann-Wachmann 1 gets brighter sometimes, for a reason that's still unknown. The comet will have quiet periods -- then periods of outburst, when it gets much brighter for days or even weeks. These outbursts can increase the comet's brightness by as much as six hundred times! Comet Schwassmann-Wachmann 1 can be seen through telescopes nearly all the time -- except when it's in the glare of the sun. It's in the sky now in early evening -- south of Antares, in the constellation Scorpius -- possibly visible through the largest amateur telescopes. Script by Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin