Space Telescope Science
If someone told you there was an object in space called "El Gordo" (Spanish for "the fat one") you might imagine some kind of planet-eating monster straight out of a science fiction movie. The nickname refers to a monstrous cluster of galaxies that is being viewed at a time when the universe was just half of its current age of 13.8 billion years. This is an object of superlatives. It contains several hundred galaxies swarming around under a collective gravitational pull. The total mass of the cluster, and refined in new Hubble measurements, is estimated to be as much as 3 million billion stars like our Sun (about 3,000 times more massive than our own Milky Way galaxy) – though most of the mass is hidden away as dark matter. The cluster may be so huge because it is the result of a titanic collision and merger between two separate galaxy clusters. Thankfully, our Milky Way galaxy grew up in an uncluttered backwater region of the universe.