http://www.sciencedaily.com/releases/2013/04/130416180032.htm
April 16, 2013 - ScienceDaily.com
Three unusually long-lasting stellar explosions discovered by NASA's
Swift satellite represent a previously unrecognized class of gamma-ray
bursts (GRBs). Two international teams of astronomers studying these
events conclude that they likely arose from the catastrophic death of
supergiant stars hundreds of times larger than the sun.
...
Using the Gemini North Telescope in Hawaii, Levan and his team obtained a
spectrum of the faint galaxy that hosted the Christmas burst. This
enabled the scientists to identify emission lines of oxygen and hydrogen
and determine how much these lines were displaced to lower energies
compared to their appearance in a laboratory. This difference, known to
astronomers as a redshift, places the burst some 7 billion light-years
away.
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