Galactic Leaders 
Our home galaxy, the Milky Way, is one of the leaders of a galactic pack: the Local Group. Its three dozen or so galaxies move through space together, tied to each other by gravity.
The Local Group has a definite hierarchy, with two leaders and a whole bunch of followers. The Milky Way is one of the leaders, while the other is the Andromeda galaxy. Both galaxies look like cosmic pinwheels, with streamers of bright stars wrapping around bright middles. Each galaxy spans more than a hundred thousand light-years, and contains hundreds of billions of stars.
But it’s tough to tell which of the two leaders is the more impressive. Andromeda is bigger, but the Milky Way is more massive.
Almost all the other members of the Local Group are companions to either Andromeda or the Milky Way. In fact, both of the big galaxies have grown so big in part by gobbling up smaller galaxies. The Milky Way is devouring several of these galactic snacks right now.
And in several billion years, the Milky Way and Andromeda may devour each other. They’re moving toward each other, and they should eventually slam together and merge to form a super galaxy.
The Andromeda galaxy is high in the east-northeast at nightfall, and soars high overhead later on. Under clear, dark skies, it looks like a faint, fuzzy star. Telescopes reveal its true nature -- a family of billions of stars -- one of the leaders of a galactic pack.
Script by Damond Benningfield, Copyright 2010