Astronomers used data from NASA’s Chandra X-ray Observatory, the Hubble Space Telescope (HST) and the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) to discover a binary star system that contains a low-mass star and a black hole.
The object known as VLA J213002.08+120904, was first observed about two decades ago and it was thought to be a distant galaxy. New measurements revealed that the source is well within our Milky Way and contains a black hole a few times the mass of our Sun that is pulling material extremely slowly from its companion star. The reason it was not classified as a black hole in the past, is that it emits only a very small amount of X-rays, while, usually, black holes attract lot of material which as it falls into the black hole, emits brightly in X-rays. As Prof. Tetarenko, first author of the relevant publication, said: “This one is so quiet that it’s practically a stealth black hole”.
Since this study only covered a very small region of the sky, probably there are tens of thousands to millions of these black holes within our Galaxy. Sensitive radio and X-ray surveys covering large regions of the sky could uncover more of these quiet black holes.
Publication: Tetarekno et al. 2016
Source: Chandra Press Room