Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2000 January 17
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V4641 Sgr: The Closest Black Hole Candidate
Credit: Robert M. Hjellming et al., VLA, NRAO

Explanation: An object many astronomers believe is a black hole has been found only 1500 light-years from Earth, making it the closest black hole candidate. Although dramatic explosions emanate from the object, it is far enough away so that we are in no danger. Pictured above, V4641 was imaged just after emitting an outburst in the radio band. Jets, which lasted only minutes, are visible. V4641 is the fourth known microquasar, a miniature version of the massive, matter spewing black holes thought to exist in the centers of galaxies. The explosions are not thought to emanate from within the black hole, a location where neither matter nor information can escape, but from around the black hole, where matter from its companion star may be heating up as it falls in. Astronomers are working to understand why V4641 acts strangely even for a black hole, as the explosions it creates fade within minutes, and appear at different times in different bands of light.

Tomorrow's picture: The Bubble Nebula

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
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& Michigan Tech. U.