Galaxies
Explore the different types of galaxies, how they evolve, and how they form the large-scale structure of the universe
Overview
Galaxies consist of stars, planets, and vast clouds of gas and dust, all bound together by gravity. The largest contain trillions of stars and can be more than a million light-years across. The smallest can contain a few thousand stars and span just a few hundred light-years. Most large galaxies have supermassive black holes at their centers, some with billions of times the Sun’s mass.
