Gamma-ray bursts (GRB) have left astronomers scratching their heads since the late 1960s when they were discovered by U.S. military satellites. Part of the mystery began to unlock when astronomers at Northwestern University detected the first observational evidence for the remnants of hypernovae, explosions hundreds of times more powerful than supernovae, last year. Hypernovae may be the possible source of GRBs, making them the most energetic events known in the Universe besides the Big Bang. .
Northwestern astronomer Daniel Wang identified two hypernova remnants in galaxy M101, also known as the Pinwheel galaxy some 25 million light years away, in April 1999. The remnants were previously thought to be supernovae remnants, but Wang detected strong X-ray emission from them which led him to believe it was an explosion much more powerful than a supernova. One nebula, MF83, has a radius of over 430 light years and is one of the largest remnants known. The other nebula, NGC5471B, is expanding very fast at a velocity of 100 miles per second. The X-ray light from these nebulae is brighter than the brightest supernova remnants known. After Wang calculated the energy needed to produce these remnants, he concluded they were most likely a result from a hypernova.
"These are two of the most unusual remnants known," Wang said. "We see that they are bright in X-ray even at a distance of 25 million light years away. They must be from spectacular explosions.".
Bohdan Paczynski, of Princeton University, first introduced the concept of a hypernova in 1998 as a why to explain GRBs. Gamma-ray bursts are brief but intense blasts of high-energy radiation. They only last for about 3 seconds, but in that brief time they can release enough energy to be more luminous than the rest of the universe. Paczynski theorized that a hypernova is most likely related to the formation of black holes. The collapse of a massive star and/or its merger with a neutron star could generate more energy than an average star explosion.
