Galaxy Clusters

space · gravity · galaxies · super massive

Hundreds of galaxies together. A galaxy cluster is like a cosmic city made of hundreds to thousands of galaxies all packed together and held by gravity. The smallest ones are called galaxy groups, but the really big ones are called clusters.

Unimaginably heavy. Galaxy clusters are so massive that they weigh between 1 quadrillion and 10 quadrillion times more than our Sun. That's like comparing the weight of Earth to the entire ocean, but way, way bigger.

Made of three things. Clusters contain galaxies you can see, super hot gas floating between them, and mysterious dark matter that we can't see but know is there because of its gravity.

The universe's largest structures. For many years, scientists thought galaxy clusters were the biggest structures in the universe until the 1980s, when they discovered even bigger superclusters that contain galaxy clusters inside them.