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Scopes watch a stellar firecracker
NASA spacecraft have spotted a peculiar star that is exploding like a cosmic firecracker. The object, a type of neutron star called a magnetar, has begun a string of powerful outbursts at a rate of several hundred an hour.
The biggest flares are so powerful that each releases more energy than the Sun does in 20 years.
Astronomers first noticed a series of modest eruptions from the star, called SGR J1550-5418 in the southern constellation of Norma, in October.
Two NASA space telescopes, Swift and Fermi, were turned on it in time to see it go off like a machine gun in January. The flares, which fired streams of gamma rays into space, happened 30,000 years ago but have just reached Earth’s neighbourhood.
Astronomer Loredana Vetere, of Pennsylvania State University, said: “At times, this remarkable object has erupted with more than 100 flares in as little as 20 minutes. The most intense flares emitted more total energy than the sun does in 20 years.”
Neutron stars are the collapsed remains of supernovas – stars that blow themselves to pieces in a cosmic suicide. They are thought to be around ten miles wide but a thimbleful of its material would weigh one hundred million tons! One has been discovered in our own neighbourhood.
Astronomers classify the type of neutron star being watched in Norma as a “soft-gamma-ray repeater”. Only five others are known. They believe the explosions are due to violent “starquakes” in the rigid outer crust of the star, caused by the strain from the magnetar’s powerful magnetic field.
Picture: An artist’s impression of a magnetar. (Image: Robert S. Mallozzi, University of Alabama in Huntsville, and NASA Marshall Space Flight Center).
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