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From: dipper@utastro.UUCP (Debbie Byrd)
Newsgroups: net.astro
Subject: StarDate: January 19 Venus and Comet Halley
Message-ID: <286@utastro.UUCP>
Date: Sun, 19-Jan-86 02:00:19 EST
Article-I.D.: utastro.286
Posted: Sun Jan 19 02:00:19 1986
Date-Received: Wed, 22-Jan-86 05:23:23 EST
Organization: U. Texas, Astronomy, Austin, TX
Lines: 34


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