dipper@utastro.UUCP (Debbie Byrd) (07/29/84)
The planet Neptune will be carefully watched by some astronomers today. We'll tell you why -- right after this. July 22 Occultation by Neptune Today the planet Neptune gets special attention from astronomers because today this faraway world passes in front of an even-more-distant star, the faint star SAO186001. This type of event is called an occultation -- Neptune is said to occult the star. In this particular case, the occultation will be well observed -- because Neptune is the only gas giant world in the outer solar system NOT known to have a system of rings. Saturn's rings have been known for centuries, since shortly after the invention of the telescope. Jupiter's ring or rings were discovered in 1979 by the Voyager spacecraft. And the dark, narrow rings of Uranus were discovered in 1977, in an event much like the one due to involve Neptune and a star today. When rings were discovered for Uranus -- just before Uranus was due to occult a star -- astronomers saw the light from the star wink off, and then return, several times before the main occultation. What was happening was just this -- the rings of Uranus were also passing in front of the star, blocking its light. Rings for Uranus and for Jupiter were a surprise. Now it would almost be a BIGGER surprise if Neptune doesn't have rings. Then we'd have to figure out why it doesn't, when all the other gas giants do. In any case, the issue will be resolved today only IF rings are discovered for the planet Neptune. Otherwise, we may have to wait until later in this decade to find out -- sometime after the launch of Space Telescope -- or when Voyager finally gets to Neptune in 1989. Script by Deborah Byrd. (c) Copyright 1983, 1984 McDonald Observatory, University of Texas at Austin