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GRB 090423 is the designation given to a gamma-ray burst first detected on April 23rd, 2009. It currently holds the distinction of being both the farthest object known in the universe, at a distance of over 13 billion light years from Earth, as well as the oldest—the burst is believed to have been triggered by the destruction of a massive star while the universe was only about 600 million years old (merely 5% of its present age).

GRB 090423 was initially detected by NASA through Swift, an orbiting observatory designed specifically to detect, pinpoint and measure data concerning gamma-ray bursts. Although the burst itself was observed by Swift as lasting only ten seconds, it's in the subsequent afterglow of longer wavelength radiation (typical of gamma-ray bursts) which provides scientists with the vast majority of their information concerning the conditions and environment of any given burst. To this end, leading astronomers from around the globe took to examining GRB 090423's afterglow, relying heavily on the largest, most advanced ground telescopes available.

It had been 17 hours since Swift first detected GRB 090423, when Professor Nial Tanvir from the University of Leicester and his team determined, by way of infrared observations using the Very Large Telescope in Northern Chile, the incredible distance at which the gamma-ray burst had occured. As Tanvir explains, "We find that the light coming from the explosion has been stretched, or redshifted, considerably by the expansion of the Universe. With a redshift of 8.2 this is the most remote gamma-ray burst ever detected, and also the most distant object ever discovered — by some way"(6). Prior to the discovery of GRB 090423, the record for the farthest known gamma-ray burst belonged to an explosion designated GRB 080913 in September 2008, which had measured a redshift of 6.7.


  1. "Most distant object in the universe spotted" by Rachel Courtland, New Scientist (April 2009)
  2. "Gamma-ray afterglow reveals new secrets" Physics World (May 21st, 2003)
  3. "New Gamma-Ray Burst Smashes Cosmic Distance Record" by Francis Reddy, NASA (April 28th, 2009)
  4. "Exploding star is oldest object seen in universe" CNN (April 29th, 2009)
  5. "Swift Gamma-Ray Burst Mission" Wikipedia
  6. "The Most Distant Object Yet Discovered in the Universe" European Southern Observatory (April 28th, 2009)
  7. "About the Swift Gamma-Ray Burst Mission" NASA (April 2nd, 2010)