V4641 Sagittarii

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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

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.

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]


  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."

External links[edit]

Coordinates: Sky map 18h 19m 21.636s, −25° 24′ 25.6″