dipper@utastro.UUCP (Debbie Byrd) (11/02/86)
Where our sun is in the Milky Way galaxy -- -- after this. November 2 The Sun's Place in the Galaxy Today's the birthday of an astronomer named Harlow Shapley. He showed that the sun doesn't lie at the center of the Milky Way galaxy. But let's back up a minute. You know that hazy-looking band you can see sometimes in a dark summer sky? That's also called the Milky Way, and when you see it, you're actually looking into the disk of our own galaxy. In 1750, an astronomer suggested that the sun was one of many stars in the galaxy. In 1785, another astronomer showed that the galaxy is shaped like a pancake, round and flat. This second astronomer -- William Herschel -- went on to say that the sun resides in the center of the galaxy. That belief persisted until early in the 20th century -- until the study of globular star clusters made by Harlow Shapley. Globular star clusters contain thousands, or even millions of stars. Because they're large and bright, we can observe them over colossal distances. In 1917, Shapley mapped the distribution of the clusters and found that they form a gigantic sphere, with most clusters densely packed at the center of the sphere. But the center of the sphere wasn't where the sun is. Then Shapley made a bold suggestion. He proposed that the clusters lie outside the disk of the galaxy and that they're centered on the galaxy's center. Today, we know he was right -- and that the sun doesn't reside in the center of the Milky Way. Instead, the center of the galaxy lies at least 25 thousand light-years inward from where we are. Script by Deborah Byrd. (c) Copyright 1985, 1986 McDonald Observatory, University of Texas at Austin