An earthquake can be a pretty awe-inspiring natural event - a testament to the sheer power and size of shifting landmass. But what about seismic activity on a star? NASA's Fermi satellite recently spotted evidence of seismic waves rippling throughout a high-energy neutron star, resulting in an intense "storm" of high-energy blasts.
The star in question, called SGR J1550-5418, is a magnetar - an incredibly dense and highly magnetized neutron star that spins at an exceptionally high speed. The typical neutron star boasts a magnetic pull trillions of times stronger than the Earth's. A magnetar, by comparison, is about 1,000 times more magnetic than that.
Within the last four decades, only 23 magnetars in all have been identified, and among these stars, only three massive flares have ever been seen. The flares were related to "starquakes," in which instability of a neutron's pressing magnetic field literally shakes its surface.
"Fermi's Gamma-ray Burst Monitor (GBM) has captured the same evidence from smaller and much more frequent eruptions called bursts, opening up the potential for a wealth of new data to help us understand how neutron stars are put together," Anna Watts, an astrophysicist at the University of Amsterdam in the Netherlands, explained in a recent release. (Scroll to Read on...)
[Credit: NASA/Swift/Jules Halpern, Columbia University]
Watts co-authored a study of SGR J1550-5418's quakes and resulting "burst storm" that was recently published in The Astrophysical Journal.
According to Watts, it takes an incredible amount of energy to convulse a magnetar. If based on Earth's seismic scale, a starquake associated with a magnetar's giant flare would reach a magnitude of about 23. The most intense earthquake ever recorded only boasted a magnitude of 9.5.
Watts and her colleagues examined 263 individual bursts detected by Fermi's GBM, finding that they "are likely twisting oscillations of the star where the crust and the core, bound by the super-strong magnetic field, are vibrating together."
"We also found, in a single burst, an oscillation at a frequency never seen before," she added.
That alone, Watts says, just goes to show how much more there is left to understand about these incredible stars. Still, her work is far from finished.
"Right now," she added, "we are waiting for more bursts - and if we're lucky, a giant flare."
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