The Hubble telescope has shown us incredible sights, including an estimated 100 billion galaxies. That’s definitely not how many are out there, though. Once we have more powerful telescopes, we’ll probably see about 200 billion. So how did all those galaxies get there? How do galaxies form?
1. We don’t know for sure.
Most galaxies formed when the universe was very, very young. For this reason, we don’t really have examples of how galaxies form and so we have to make an educated guess based on computer models.
2. Gas clouds form high mass stars.
Based on simulations, what we think happened is that clouds of gas and dust that were floating out in the early universe began to come together as high-mass stars. When enough of these stars pull together, they become protogalaxies and star collecting gas and dust.
3. As more stars cluster together, the gravity strengthens.
Galaxies are held together by gravity, and it takes a lot of stars to create enough gravity for an entire galaxy to coalesce. Eventually, the gravity becomes so strong that the galaxy begins to spin around a common center of mass. And tada! A fully formed galaxy is born. At least, that’s the basics of what we think happens.