dipper@utastro.UUCP (Debbie Byrd) (03/31/85)
Our sun is a star revolving around the center of the galaxy. More -- after this. March 31 The Galactic Carousel and the Cosmic Year Our Milky Way galaxy is a flattened disk of stars -- with long starry arms spiraling away from a bright bulging center. Our sun is just one of many hundreds of billions of stars in the Milky Way. Like all the other stars in the galaxy, the sun -- with its family of planets including Earth -- revolves around the galactic center. One circuit of the galaxy takes us about two hundred and forty million years. As the sun circles the center of the galaxy, it also bobs up and down with respect to the galactic plane -- the disk of the galaxy, where most of the stars are. The sun moves up and down -- and around -- like a wooden horse on a carnival carousel. One or two million years ago, the sun crossed the galactic plane moving northward, toward the north pole of the galaxy. About ten million years from now, after gradually slowing down, the sun will reverse direction -- travel back towards the plane of the galaxy -- and cross back to the other side. A complete up and down cycle takes about 66 million years -- so during one trip around the galaxy, the sun crosses the galactic plane about eight times. Look low in the south in the evening at this time of year -- and you'll be looking backwards in our journey around the center of the galaxy. Again, it takes our sun about two hundred and forty million years to go once around the galactic center -- a time interval which astronomers call the cosmic year. Script by Diana Hadley and Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin
gwhawkins@watrose.UUCP (gwhawkins) (04/07/85)
> One or two million years ago, the sun crossed the galactic plane moving > northward, toward the north pole of the galaxy. About ten million > years from now, after gradually slowing down, the sun will reverse > direction -- travel back towards the plane of the galaxy -- and cross > back to the other side. A complete up and down cycle takes about 66 > million years -- so during one trip around the galaxy, the sun crosses > the galactic plane about eight times. > Script by Diana Hadley and Deborah Byrd. > (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin Sorry for not really knowing what I'm talking about, but isn't there some question at the moment as to where we are on this carousel? I heard on the CBC radio program Quirks and Quarks that the up down cycle could be as short as 36 million years and that we are due to cross the galactic plane again in the next 1 to 3 million years. Admittedly, the gentleman doing the explaining was using this information to verify another theory. Was he out to lunch or is there really a great deal of uncertainty in calculating this cycle? larry fast (Universty of Waterloo) broadcasting from exile PS On behalf of the readers of this group, I'd like to thank Diana Hadley, Deborah Byrd and anyone else involved in bringing us our regular Astro-fix.