Spiral galaxies like the Milky Way are surprisingly rare in our galactic neighborhood. The Milky Way, for example, is a spiral galaxy because of the way that stars, dust, and gas spiral out from the center of the galaxy. But spiral galaxies like ours are surprisingly rare in our galactic neighborhood, and for years, astronomers have wondered why since the 1960s. The simulation showed that galaxies in dense clusters, like the one our Milky Way calls home, experienced frequent collisions and mergers. For example, when two spiral galaxies collide, it's thought to create what's called an elliptical galaxy.

---

Persons: —, Carlos Frenk Organizations: Service, Institute, Durham University