A team of British and French astronomers may have observed the first black hole that has an intermediate mass. Known as HLX-1, the object is estimated to have a mass of at least 500 solar masses.
The letter, written by a team of British and French astronomers, does not state that they have found an intermediate mass black hole—one that could be termed just right—but that they have found an object where most other explanations fail to explain its behavior.
The object, 2XMM J011028.1-460421 or (more conveniently) HLX-1, is a source of ultraluminous X-rays near the spiral galaxy ESO 243-49. These X-rays have been postulated to be the product of an intermediate mass black hole, one between 100 and 10,000 solar masses, but to date no candidate object has been widely accepted.