Massive space blast aims at Earth

When an explosion is visible on Earth and it originates halfway across the universe, you know you’ve seen something big.
Two international teams of astronomers have gathered data on the brightest gamma-ray burst humans have ever recorded.

Its first, brief, visible flash reached an estimated magnitude 5.6, which is near the limit of human vision, but well within the capability of a decent pair of binoculars. The event, which occurred March 19, was 200 million times brighter than its host galaxy, according to Alex Filippenko, a University of California at Berkeley astronomer. The blasts are thought to result from the merger of two neutron stars, or from the explosion of a massive star and its immediate collapse into a black hole.

Material falling into the black hole energizes powerful, tightly focused jets that hurtle out along the hole’s rotation axis. In this case, the beam pointed directly toward Earth, which accounted for its apparent brightness.

A second team used the information to try to determine the mechanism driving the emissions – it’s the first time scientists have seen a blast’s three emission phases in one event. Dr. Filippenko notes that, in principle, this detection shows that astronomers may be able to spot these blasts at far greater distances, corresponding to a time when the universe was only a few hundred million years old.

The results appear in today’s issue of the journal Nature, as well as in a longer paper accepted by the Astrophysical Journal.

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