dipper@utastro.UUCP (Debbie Byrd) (01/19/86)
Today the planet Venus is directly behind the sun -- with a ringside seat on Comet Halley. More -- after this. January 19 Venus and Comet Halley Today Venus is traveling directly behind the sun from our world -- passing a position called superior conjunction by astronomers. When it's behind the sun, Venus can't be seen from our world. And yet this particular conjunction of Venus is interesting -- because Venus is now in the same region of the solar system as Comet Halley. Halley is now in the west after sunset. With each passing day it gets a little closer to its own conjunction with the sun -- when, like Venus, Halley will be impossible to see from our world. Halley will disappear behind the sun later this month. It will be gone from our sky -- across the solar system from Earth -- some 150 million miles away. That's too bad, because on February 9, Halley will reach perihelion -- its closest point to the sun in 76 years. When Halley reaches perihelion, Earth will be far away -- but Venus will be only 36 million miles from the comet. So though we won't see Halley at perihelion, something we built will see it -- a NASA spacecraft orbiting Venus. Pioneer Venus has been orbiting our sister world since 1978. By now, it should have already used some of its instruments to scan the comet -- and it'll turn toward the comet again soon -- to create a picture of Halley in ultraviolet light. Nobody on Earth will see Halley when the comet is closest to the sun. But we'll have a ringside seat on this event -- through the eyes of Pioneer Venus. Script by Deborah Byrd. (c) Copyright 1985, 1986 McDonald Observatory, University of Texas at Austin