dipper@utastro.UUCP (Debbie Byrd) (06/22/85)
This is the anniversary of the discovery of Pluto's moon. More -- after this. June 22 A Moon for Pluto On this date in 1978, astronomers made one of the most unexpected discoveries in the solar system. They found a big moon for the small outer planet, Pluto. Pluto's moon was a surprise, partly because Pluto itself was long thought to be an escaped moon of Neptune. Now it's more likely that Pluto never orbited Neptune at all. Instead, some astronomers think that, besides Pluto and its moon, there are other small bodies in the outer solar system -- that remain to be found. Pluto's moon was discovered by an astronomer at the U.S. Naval Observatory. In some photographs taken with a telescope, James W. Christy noticed a bulge on Pluto -- a giant bulge far too large to be an ordinary surface feature. It wasn't a surface feature -- it was Pluto's moon. The pair appeared attached in the photograph because they're close to each other -- and very far away from us. The moon was given the name Charon, for the mythological ferryman who rowed souls across the River Styx, into Pluto's underworld. This year, Pluto and its moon began eclipsing each other every few days, as seen from our vantagepoint on Earth. The eclipses of Pluto and Charon will let us study these two worlds. We'll learn more about their orbits -- and thereby their masses -- and also get information on light and dark areas on the surfaces of the two worlds. The eclipses of Pluto and Charon will give the next-best-thing to spacecraft data on the pair -- a good thing, since no spacecraft is planned to visit Pluto at least through the end of this century. Script by Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin