dipper@utastro.UUCP (Debbie Byrd) (02/17/86)
On this date last year, observers caught the first definite eclipse of Pluto by its tiny moon. More -- after this. February 17 Anniversary of an Eclipse Pluto is so faraway that, through telescopes, it looks just like a star. Still, in 1978 a moon was discovered for Pluto. The moon is even smaller than the planet -- though the two are so nearly the same size that they're sometimes called a double world. Pluto's moon was given the name Charon -- and soon after its discovery an exciting prediction was made. Based on their orbits, it appeared that these two faraway worlds would begin a series of eclipses of each other sometime around 1982. Astronomers watched for light from the Pluto/Charon system to decline -- indicating an eclipse in progress. They watched for a couple of years in fact -- until finally, on this date last year, they saw the first eclipse of Pluto by Charon. Pluto and its moon orbit the sun only once every 248 years. There are just two occasions in this long orbit where Pluto and Charon are oriented with respect to Earth such that we see them pass in front of each other. One such occasion is now. The eclipses of Pluto and Charon will continue for about five years. They'll reveal a great deal about these two remote worlds -- about their orbits, masses, and maybe even their surface features. Then the eclipses will stop as seen from the vantage point of Earth. Astronomers will have to wait more than a century for them to begin again. It so happen that the eclipses were seen to begin last year just one day before the anniversary of the discovery of Pluto. More on that subject -- tomorrow. Script by Deborah Byrd. (c) Copyright 1985, 1986 McDonald Observatory, University of Texas at Austin