dipper@utastro.UUCP (Debbie Byrd) (10/18/85)
You can see star clusters and celestial clouds using just your eye. More -- after this. October 18 Naked-eye Stargazing The universe contains lots of stars. But they don't seem to like to go it alone. Instead stars group into galaxies. If you think of the universe as a country, then galaxies are its cities. Each galaxy-city glitters with the light of billions of stars. Our sun is just one of hundreds of billion of stars in the Milky Way galaxy. All the stars we see in the night sky reside within the boundaries of this galaxy. We don't see stars belonging to any other galaxies. With only a few exceptions, we don't see external galaxies at all using just the eye. But, with the eye alone, we can see some interesting things in the sky -- for example, star clusters and vast clouds of gas. Star clusters are families of stars bound together by mutual gravity. A famous star cluster is the Pleiades, or Seven Sisters, which is now back in the eastern sky every evening. The Pleiades look like a tiny, misty dipper. But this is really a cluster containing hundreds of stars. These stars probably were born from a single cloud of gas. With the eye alone, we can also see gas clouds residing in the space between stars in our galaxy. The Great Nebula in the constellation Orion is one. It's up now by about midnight. It looks to the naked eye like a fuzzy star. But it's really a great gas cloud containing billions of times as much mass as the Earth. When you look at this cloud -- which seems so small from Earth -- you're actually seeing a star factory -- a place where new stars are born. Script by Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin