V4641 Sagittarii

V4641 Sagittarii (V4641 Sgr) 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.

V4641 Sagittarii
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Sagittarius
Right ascension 18h 19m 21.63s
Declination −25° 24′ 25.8″
Other designations
V4641 Sagittarii, V4641 Sgr, GSC 06848-03786, SAX J1819.3-2525, 2MASS J18192163-2524258, AAVSO 1813-25B, XTE J1819-254
Database references
SIMBADdata

In 1999 a violent X-ray outburst revealed it to contain a black hole.[1] At the time, it was considered to be the closest known black hole to Earth, at a distance of approximately 1,600 light-years (490 pc). Later observations showed it to be at least 15 times farther away.[2]

References
  1. "Dramatic Outburst Reveals Nearest Black Hole". National Radio Astronomy Observatory. Retrieved 2008-08-30.
  2. A Black Hole in the Superluminal Source SAX J1819.3-2525 (V4641 SGR), 2001: "Finally, we find a distance in the range 7.40 ≤ d ≤ 12.31 kpc (90% confidence), which is at least a factor of ≈ 15 larger than the initially assumed distance of ≈ 1,600 light-years/500 pc."


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