Our home galaxy, the Milky Way, is the hub of a galactic empire. It’s not the kind with death stars and Jedi knights, though. Instead, it’s an empire of smaller galaxies. About 50 of these “dwarf” galaxies orbit the Milky Way, held in place by its powerful gravity.
As those numbers suggest, dwarf galaxies are the most common type of galaxy in the universe. They outnumber giants like the Milky Way by a wide margin. But it takes a whole mess of them to add up to much. In fact, the Milky Way is more massive than all the dwarf galaxies it commands combined.
Some of these cosmic “puffballs” may have been pulled out of larger galaxies by encounters between big galaxies. But most of them probably formed in the early universe — the very first collections of stars.
The galaxies were packed together tightly, so many of them began to merge. That’s probably how most of the big galaxies took shape — through mergers between the little guys.
And that process continues today. We see many large galaxies gobbling up the dwarfs. That includes the Milky Way. There’s evidence that it’s consumed quite a few smaller galaxies during its long lifetime. And astronomers have discovered one galaxy that’s being consumed by the Milky Way now, and others that were pulled in fairly recently. All of them will lose their galactic identity — their stars pulled away from them by the mighty Milky Way.
We’ll have more about dwarf galaxies tomorrow.
Script by Damond Benningfield