dipper@utastro.UUCP (Debbie Byrd) (05/19/85)
The night sky this month contains a vast collection of galaxies. More on the Virgo Supercluster -- when we come back. May 19 The Virgo Supercluster During the month of May, the plane of the Milky Way galaxy lies more or less flat around the horizon during the evening hours. So overhead this month we have a clearer view into the space beyond our galaxy -- because the disk of the galaxy isn't in the way -- and so there's less material -- fewer stars, and less gas and dust -- to block the view. Looking overhead in May, astronomers with telescopes see a great supercluster of galaxies. Thousands of galaxies are hidden in the depths of the May night. These galaxies can't be seen just by looking up, because they're too faint. But they exist -- thousands of galaxies -- each one a collection of billions of stars -- and each bound to the others by gravity. The supercluster of galaxies spans a region of space some hundred million light-years across. The gravitational center of the supercluster is thought to be located in the direction of the constellation Virgo -- so we call it the Virgo supercluster -- or the local supercluster -- because we're in it, too. The heart of the supercluster may lie about 40 million light-years away. And yet we also belong to this collection of galaxies -- our Milky Way galaxy is a member of this supercluster. The Milky Way is thought to be located in an outlying region of the supercluster -- which is why we can look mainly toward one direction of space to see most of the rest of it -- in the direction of space that our night sky faces in May. Script by Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin