The Big Picture: Hubble peeks at the Milky Way's densest star cluster

Some parts of space are a little more crowded than others. The Arches Cluster, located 25,000 light-years from Earth, is currently the densest known star cluster in the Milky Way. For comparison, if you measured the distance between our sun and its nearest star, and used that as a radius for a section of the Arches Cluster, you would find more than 100,000 stars twinkling back at you. These balls of gas burn brightly -- NASA says 150 are among the brightest it's ever recorded -- which limits their natural lifespan to a few million years. Once their nuclear fuel has been depleted, they explode in breathtaking supernovas which create abnormally high volumes of heavy elements in the gas between the remaining stars. The image above was captured by the Hubble Space Telescope in infrared; due to enormous dust clouds, the cluster is otherwise obscured and difficult to observe.