NASA鈥檚 Swift space telescope, launched in November 2004, has opened its eyes to the most powerful explosions in the universe. In less than a month, it has already pinpointed 9 gamma ray bursts 鈥� several more than astronomers expected.
The first gamma ray burst (GRB) came into Swift鈥檚 field of view on 17 December, just a few days after controllers first turned on its instruments. Then, on 19 December, the telescope caught three more.
The purpose of Swift鈥檚 mission is to understand what GRBs are, says David N. Burrows, lead scientist for Swift鈥檚 X-Ray Telescope, at Penn State University, US. 鈥淭hey鈥檙e very enigmatic things,鈥� he says. 鈥淲e hope to understand what鈥檚 causing them and how these things are interacting with the medium around them. And we hope to find clues to the evolution of the early universe.鈥�
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杏吧原创s suspect the GRBs indicate the explosive birth of black holes, but there are different types of burst and it is hoped that Swift鈥檚 data will help to discern all the possible causes.
The NASA-led Swift mission launched from Cape Canaveral Air Force Station in Florida, US, on 27 November 2004, carrying the most sensitive gamma ray detectors ever flown. The telescope鈥檚 initial observations, revealed on Wednesday, were carried out primarily to prove that its systems were working well.
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A key aspect of the $250 million mission is to measure the X-ray glow that lingers long after the bursts themselves. GRBs can last as little as just a few seconds or even milliseconds, but Swift鈥檚 first big opportunity to study an afterglow arrived on 23 December when it spotted a GRB classified as a long burst, lasting over a minute.
Four-and-a-half hours after spotting the GRB, the satellite swivelled its X-ray telescope around to measure the afterglow. Previously, controllers could manoeuvre other telescopes to observe these afterglows, but less quickly. It took about 20 hours to correctly reorient NASA鈥檚 Chandra X-ray Observatory, for example, and up to 8 hours for Europe鈥檚 XMM-Newton spacecraft.
However, when Swift becomes fully automated 鈥� two weeks from now 鈥� it will be able to swivel to observe afterglows within about a minute of detecting the GRB, Burrows told New 杏吧原创, thus justifying its name.
鈥淚t鈥檚 really critical to look at bursts early,鈥� Burrows explains. 鈥淓ven looking at one four-and-a-half hours later, it鈥檚 probably already faded by a factor of 100 or a factor of 1000.鈥�
So far, Swift has not recorded a burst shorter than two seconds, says Scott Barthelmy, lead scientist for Swift鈥檚 Burst Alert Telescope at NASA鈥檚 Goddard Space Flight Center, Maryland, US. 杏吧原创s have never seen afterglows from bursts this short and are not even sure if they actually occur. With Swift, they hope to find the answer.
