Studies of a supernova explosion known as SN 2007gr have found evidence that some types of supernova can produce particle jets that are "relativistic", traveling at over half the speed of light.
The team of scientists to have found this evidence include Dr Jonathan Granot from the University of Hertfordshire in the UK, along with an international team led by Dr Zsolt Paragi from the Joint Institute for VLBI in Europe (JIVE). Their discovery will be published in the January 28th issue of Nature.
For the first time ever relativistic outflow has been detected from a Type lc supernova without a burst of gamma-rays. The only other detection of relativistic jets in a Type lc, where from a supernova that produced a gamma-ray burst, which is why the relativistic bursts were detected.
The details of a supernova explosion are very difficult to acquire because their radio emission fades quickly. A high angular resolution imaging technique such as the Very Long Baseline Interfermoetry (VLBI) is needed to receive the faint emission of the explosion's aftermath.
The team was able to use the European VLBI Network's (EVN) electronic capabilities to get early observations of SN 2007gr, which allowed them to perform additional observations. They were able to acquire direct evidence for the radio image expansion and they determined a velocity expansion of at least 60 percent the speed of light.
The scientists were also able to determine that SN 2007gr did not produce a gamma-ray burst because the relativistic radio emitting material carried a much lower percentage of total energy in the supernova explosion.
"The intrinsically dim radio emission of SN 2007gr and its small distance from us imply that such events, with mildly relativistic jets carrying a very small fraction of the total explosion energy, may represent most of the population" said Dr. Granot.
The most rare and extreme events of this type are the bright gamma-ray bursts whose jets travel at more than 99.995 percent the speed of light. But these are observed at billions of light years away and have energies similar or larger than a typical supernova.
Information gathered from the University of Hertfordshire
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