dipper@utastro.UUCP (Debbie Byrd) (05/17/85)
The month of May is the best time to try to imagine our solar system's movement through the Milky Way galaxy. More -- after this. May 17 The Missing Milky Way Stargazers may notice something missing this month -- the starlit band of the Milky Way is NOT in the evening sky. In the evening in late summer, the Milky Way arcs across the sky. It looks something like a long band of clouds -- glowing faintly -- in reality composed of myriad stars whose light blurs together when seen over a colossal distance. These stars all are located in the flat disk of the Milky Way galaxy -- the island of stars that contains our own sun. We're in the disk of the galaxy, too -- it always surrounds us in space. But we don't see the Milky Way in the evening this month because, in May, our evening sky faces up away from the galactic disk. This month, the starlit band of the Milky Way lies as flat around the horizon as it can during the evening hours. If you stand outside some evening in May -- stretch out your arms -- and spin yourself around like a top -- you'll be spinning in the same plane as the vast disk of the Milky Way. Then if you face northeast, you'll be facing the direction our own solar system travels through the galaxy -- as our sun progresses in its 250-million-year circuit around the galactic center. The speed of the sun on this journey is very great. Our sun and Earth, and you along with them, all are moving around the center of the galaxy -- right now -- at about 150 miles PER SECOND! Script by Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin