V4641 Sagittarii


V4641 Sagittarii is a variable X-ray binary star system in the constellation Sagittarius. It is the source of one of the fastest superluminal jets in the Milky Way galaxy.
In 1999 a violent X-ray outburst revealed it to contain a black hole. At the time, it was considered to be the closest known black hole to Earth, at a distance of approximately. Later observations showed it to be at least 15 times farther away.