dipper@utastro.UUCP (Debbie Byrd) (11/12/85)
What happens when galaxies collide? We'll tell you about it -- after this. November 12 When Galaxies Collide On its grandest scale, the universe consists of galaxies -- huge collections of stars that are like islands in a sea of nearly empty space. There are billions of galaxies -- with lots of space in between. So the galaxies don't meet each other all that often. But galaxies do collide. While looking outward into the universe, astronomers can see evidence for a number of collisions between galaxies. Galaxies aren't solid objects -- they're made primarily of stars. But even though each galaxy may contain hundreds billions of stars encounters between galaxies DON'T involve collisions between stars in the galaxies. The reason is that stars in galaxies are incredibly small compared to the gigantic distances between the stars. When galaxies collide, there's plenty of room for the stars within them to pass each other by. But that doesn't mean there's no chaos when galaxies collide -- because the stars do affect each other gravitationally. Collisions between galaxies often distort the original shapes of the galaxies. Usually, the larger galaxy captures many of the stars in the smaller one. Sometimes long tails of stars are pulled out from the galaxies -- so that one pair of colliding galaxies has been nicknamed "the mice" by astronomers. And, besides stars, many galaxies also contain quantities of tenuous gas. During galactic collisions, the gas in galaxies interacts -- and this interaction tends to generate new stars. These new stars last for millions of years -- and we here on Earth can observe them! Script by Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin