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

The Farthest Explosion Yet Measured
Credit: H. Pedersen (U. Copenhagen) et al., FORS1, VLT Antu, ESO

Explanation: It happened so far away that common human distance measures are inadequate to describe it. Furthermore, astronomers do not even claim to know exactly what happened. What is known is that satellites across our Solar System reported on 2000 January 31 a tremendous explosion of gamma rays had occurred towards some previously uninteresting direction. Soon one of the largest optical telescopes on Earth, a VLT in Chile, began to peer in the direction of the gamma ray burst. The VLT not only recorded an optical counterpart, shown above, but also was able to estimate that the cosmologically-induced redshift was an astonishing 4.5 -- placing GRB000131 farther across the universe than any explosion so measured. This vast distance indicates that GRB000131 occurred just as galaxies like our Milky Way were forming, and so qualifies gamma ray bursts as unique probes of this ancient epoch. This result bodes well for the recently launched HETE-2 satellite, which may record and help place more explosions in this distant and mysterious time-period of our universe.

Tomorrow's picture: North is Down

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
NASA Technical Rep.: Jay Norris. Specific rights apply.
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& Michigan Tech. U.