GRB 090423

GRB 090423

Event type	Gamma-ray burst
Date	c. 13 billion years ago (detected 23 April 2009, 07:55:19 UTC)
Duration	c. 10 seconds
Instrument	Swift
Constellation	Leo
Right ascension	09h 55m 33.08s
Declination	+18° 08′ 58.9″
Distance	c. 30 billion ly
Redshift	8.0 ≤ z ≤ 8.3
Other designations	GRB 090423A, GRB 090423, Fermi bn090423330
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[edit on Wikidata]

GRB 090423 was a gamma-ray burst (GRB) detected by the Swift Gamma-Ray Burst Mission on April 23, 2009, at 07:55:19 UTC whose afterglow was detected in the infrared and enabled astronomers to determine that its redshift is z = 8.2, making it one of the most distant objects detected at that time with a spectroscopic redshift (GN-z11, discovered in 2016, has a redshift of 11).

A gamma-ray burst is an extremely luminous event flash of gamma rays that occurs as the result of an explosion, and is thought to be associated with the formation of a black hole. The burst itself typically only lasts for a few seconds, but gamma-ray bursts frequently produce an "afterglow" at longer wavelengths that can be observed for many hours or even days after the burst. Measurements at these wavelengths, which include X-ray, ultraviolet, optical, infrared, and radio, enable follow-up study of the event.

The finite speed of light means that GRB 090423 is also one of the earliest objects ever detected for which a spectroscopic redshift has been measured. The universe was only 630 million years old when the GRB occurred, and its detection confirms that massive stars were born and dying even very early on in the life of the universe. GRB 090423 and similar events provide a unique means of studying the early universe, as few other objects of that era are bright enough to be seen with today's telescopes.