On Aug. 22, 2008, NASA's Swift satellite reported multiple blasts of radiation from a rare object known as a soft gamma repeater, or SGR, some 15,000 light years away. This ancient stellar remnant -one of the totally weird stars of this awesome ongoing hit movie we call the cosmos- is one the most magnetized objects in the universe. Only 15 are known to exist.
Astronomers think the eruptions of SGRs arise from the most highly magnetized objects in the universe -- magnetars, or neutron stars -- the crushed cores of exploded stars -- that, for reasons not yet known, possess ultra-strong magnetic fields. With fields 100 trillion times stronger than Earth’s, a magnetar placed half the moon’s distance would wipe the magnetic strips of every credit card on the planet.
"Magnetars allow us to study extreme matter conditions that cannot be reproduced on Earth," said Kevin Hurley, a team member at the University of California, Berkeley.
Astronomers have been conducting in-depth studies of these eruptions using the European Space Agency's XMM-Newton and International Gamma-Ray Astrophysics Laboratory (INTEGRAL) satellites.
The object, designated SGR 0501+4516, was the first of its type discovered in a decade and is only the fifth confirmed SGR. "Some sources are extremely active, but others can be quiet for a decade or more," said Nanda Rea, of the University of Amsterdam. "This suggests many members of this class remain unknown."
SGR 0501+4516 was only discovered because its outburst gave it away. Astronomers think an unstable configuration of the star's magnetic field triggers the eruptions. "Once the magnetic field resumes a more stable configuration, the activity ceases and the star returns to quiet and dim emission," Rea said.
Twelve hours after Swift pinpointed SGR 0501+4516, XMM-Newton began the most detailed study of a fading magnetar outburst ever attempted. The object underwent hundreds of small bursts over a period of more than four months. Only five days after the initial eruption, INTEGRAL detected X-rays from the object that were beyond the energy range XMM-Newton can see. It's the first time such transient high-energy X-ray emission has been detected during an SGR's outburst phase. This emission disappeared within ten days of the outburst.
Posted by Casey Kazan -adapted from NASA materials.
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