National Aeronautics and Space Administration

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Fermi's Gamma-ray Burst Monitor detected a rapid-fire "storm" of high-energy blasts from a highly magnetized neutron star, also called a magnetar, on Jan. 22, 2009. Now astronomers analyzing these data have discovered underlying signals related to seismic waves rippling throughout the magnetar.

Such signals were first identified during the fadeout of rare giant flares produced by magnetars. Over the past 40 years, giant flares have been observed just three times -- in 1979, 1998 and 2004 -- and signals related to starquakes, which set the neutron stars ringing like a bell, were identified only in the two most recent events.

Neutron stars are the densest, most magnetic and fastest-spinning objects in the universe that scientists can observe directly. Each one is the crushed core of a massive star that ran out of fuel, collapsed under its own weight, and exploded as a supernova. A neutron star packs the equivalent mass of half-a-million Earths into a sphere about 12 miles across, roughly the length of Manhattan Island in New York City.

While typical neutron stars possess magnetic fields trillions of times stronger than Earth's, the eruptive activity observed from magnetars requires fields 1,000 times stronger still. To date, astronomers have confirmed only about a couple of dozen magnetars.

» https://www.nasa.gov/content/goddard/nasas-fermi-satellite-finds-hints-of-starquakes-in-magnetar-storm