Star antics

astronomers re-examining data collected 12 years ago when supernova 1987 a exploded say the new understanding only serves to bring them one step closer to proving a link between the dramatic gamma-ray bursters and exploding stars. The giant dying star had jettisoned stellar debris in a narrow jet moving at close to the speed of light.

sn 1987 a , the brightest supernova recorded in more than 400 years, created a sensation when it appeared in a neighbouring galaxy, the large Magellanic Cloud. Peter Nisenson and Costas Papaliolios of the Harward-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, made high-resolution images of the exploding star 30 and 38 days later.

These images showed a spot with about a tenth of the brightness of the supernova about 17 millionths of a degree away. At the time, scientists published papers about this spot, Nisenson says, but they never reached any concensus on what it was.

Using state-of-the-art image-processing techniques, Nisenson and Papaliolios have now reanalysed their images and have found another less bright spot on the other side of the supernova, about 42 millionths of a degree away. "The two spots and the supernova were aligned, strongly suggesting we were seeing a two-sided jet emerging from the explosion," says Nisenson. Their results, which will appear later this year in Astrophysical Journal Letters, suggests that matter was ejected by the explosion in a jet moving almost as fast as light.

In January, another jet firing off directly towards the Earth coincided with a powerful gamma-ray burst. ( This Week , April 3, p5). The source of such bursts -- powerful flashes of gamma-rays from the edge of the visible Universe -- has been a matter of debate. But if supernovae creates jets, as a new results suggest, this would provide evidence that the sources of gamma-ray bursters and powerful explosions of stars are one and the same thing.

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