Galaxies are tremendous clusters of billions to trillions of stars, and are where the majority of G stars reside. If you’re fortunate enough to have a dark night sky, you will be able to see a section of our own galaxy, the Milky Way, as a ribbon of stars stretching across the sky. The Milky Way is estimated to be roughly 100,000 light years across, containing some 100 billion stars, and is probably a barred spiral rather than the classic swirl we think of as a galaxy. Our nearest galactic companion, the Andromeda Galaxy, is even bigger, containing up to a trillion stars, but how do these massive structures come to form?
There are two major shapes that a galaxy can form. Elliptical galaxies are fuzzy clouds of stars, whereas…