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Some baby black holes give boost, but no burst


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A pair of papers that appear in this week's edition of Nature report onsome interesting astrophysical observations. Two teams from differentcontinents have found supernovae that have an anomalousfeature: matter is moving away from them at significant fractions of thespeed of light—0.60c and 0.86c. The well known explosion dynamics of a supernova shouldn't produce that sort of acceleration; in a typical supernova event, matter shouldn't reach velocities muchbeyond three percent the speed of light.

Speeds this great are often associated with gamma ray bursts, but these observations were missing that key component."In every respect, these objects look like gamma-ray bursts—exceptthat they produced no gamma rays," said Alicia Soderberg, lead authorof one of the papers. Her team examined SN2009bb, a supernova in the spiral galaxy NGC 3278, nearly 130 millionlight years from Earth. The other team examined SN 2007gr, a supernova in spiral galaxy NGC1058, a scant 35 million light years from Earth.

Using NASA records of known gamma ray bursts, the teamsattempted to find an event that had a spatial and temporal correlation with the supernovae, but none wasidentified. Typical gamma ray bursts are thought to be the result ofthe acceleration of matter by a black hole, with the matter reaching nearly 99 percent the speed of light. The fast-moving matter here suggests that these supernovae are powered in part by a nascent blackhole at the center left behind after the core collapse.

Casting a wider net for nearby supernovae suggest that these'central engine' driven type Ib/c supernovae are fairly rare, onlyaccounting for about one percent of all cases. However, the workprovides a new tool for astronomers to be able to detect them in the future. "These observations are the first to show somesupernovae are poweredby a central engine," Soderberg said. "These new radio techniques nowgive us a way to find explosions that resemble gamma-ray bursts withoutrelying on detections from gamma-ray satellites."

Nature,2010. DOI: 10.1038/nature08714

Nature,2010. DOI: 10.1038/nature08713

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