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 19
See Explanation.  Clicking on the picture will download 
 the highest resolution version available.

A Big Black Hole Floats By
Credit: David H. Bennett (Notre Dame) et al., WFPC2, HST, NASA

Explanation: A black hole glides silently through space. Is there any way to know it's there? Until last week, all objects that might be black holes in our Galaxy were part of binary star systems. There, gas from the companion star was hypothesized to swirl around the black hole, heat up, and emit X-rays before falling in. Last week, however, analysis was released of a mysteriously dark object that floated in front of a distant background star, dramatically increasing this star's light by the lens effect of its gravity, as pictured above. The high mass and low light of this strange lens have astronomers guessing they might just have detected a lone black hole, weighing in at six times the mass of our Sun. The existence of isolated black holes is not in itself surprising, as they should be the end result of the cores of massive stars.

Tomorrow's picture: X-Rays From The Galactic Center

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
NASA Technical Rep.: Jay Norris. Specific rights apply.
A service of: LHEA at NASA/ GSFC
& Michigan Tech. U.