dipper@utastro.UUCP (Debbie Byrd) (07/07/85)
When a planet passes in front of a star -- that's an unusual event! More -- when we come back. July 7 Occultation by Venus On today's date in the year 1959, a rare celestial phenomenon took place. A pinpoint of light in the night sky was temporarily covered over by a second shining light. It was an event that astronomers call an occultation, when one celestial body is seen to pass in front of another. In this case, it was a rare kind of occultation -- of a star by a planet. The star was Regulus in the constellation Leo. And the planet was Earth's next-door neighbor, Venus. Venus is about the same size as the Earth. And Regulus is really hundreds of times larger -- about five times the diameter of our sun. But Venus is millions of times closer to us -- and although it looks like a point of light to the naked eye, it's more like a tiny moon when seen through a telescope. On the other hand, at 85 light-years away, Regulus remains a pinpoint even through a telescope -- which is why the small planet Venus could blot out the giant star for about 10 minutes. Occultations are common -- but nearly all of them take place when the moon covers up a star. An occultation of a star by a planet is extremely rare, but when it does occur, it gives scientists a chance to conduct earthbound studies of the atmosphere of the planet. Venus won't occult another star as bright as Regulus for at least several centuries. Luckily, though, we no longer need the occultations to learn about the atmosphere of Venus -- Soviet and U.S. spacecraft are doing the job nicely. Script by Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin