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An Explosion in Deep Space
As NASA's Swift satellite intently probed the universe for gamma-ray bursts, or GRBs, on April 23 of 2009, the craft detected the most distant space object ever to be found. Named for the date of its discovery, GRB 090423 was the very bright, intense explosion caused by a dying star, which usually results in the formation of a black hole. Scientists say that the star that caused the burst died when the universe was about 630 million years old, but it is only just now that the light has reached Earth.
It was 3:55 a.m. EDT when Swift trained its telescopes on the explosion that lasted for ten seconds, and in a matter of a few hours, ground telescopes examined the wavelengths of the afterglow. An afterglow is formed when jets of gas emerge--nearly at the speed of light--from the core of the dying star and heat the other gases surrounding the star. Scientists used the data to determine that GRB 090423 had a redshift of 8.2, while the previous record-holder had a redshift of 6.7. This placed the explosion at 13.035 billion light years away from Earth.
Scientists knew fairly quickly that GRB 090423 was a very distant gamma-ray burst because it lacked much visible light, according to Edo Berger at Harvard University. After a certain distance through space, visible light is altered so that it appears as longer infrared rays instead.
Because GRB 090423 is the farthest object we have detected--making it one of the few objects we have observed that lays on the outskirts of the universe--this explosion offers new prospects of studying what the early universe was like.
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