The Hubble Space Telescope recently spied a cluster of young blue stars surrounding a rare mid-weight black hole that suggests the black hole was once at the center of a dwarf galaxy.
Astronomers think this galaxy was torn apart by the gravity of a larger host galaxy that it orbited. The violent encounter would have stripped away most of the dwarf galaxy’s stars, but it also could have compressed the gas around its central black hole, triggering a new wave of star formation. It is these new stars that Hubble recently saw signs of. The observations suggest that the young stars must be less than 200 million years old, meaning the collision between the parent galaxy and its dwarf likely occurred around that time. According to researchers the black hole, called HLX-1 (Hyper-Luminous X-ray source 1), is scientifically interesting. When scientists discovered HLX-1in 2009, it was the first intermediate-mass black hole known. Scientists think it may represent a class of middleweight black holes that are the building blocks for the supermassive black holes lurking at the center of most large galaxies, including our own Milky Way.This specimen contains the mass of about 20,000 suns, and is located roughly 290 million light-years from Earth. In comparison, the supermassive black hole at the center of the Milky Way is as massive as 4 million suns. By studying this rare middleweight black hole, scientists hope to learn more about how they form.