Michael Schirber at Space.com:
The biggest starquake ever recorded resulted in oscillations in the X-ray emission from the shaking neutron star. Astronomers hope these oscillations will crack the mystery of what neutron stars are made of.
On December 27, 2004, several satellites and telescopes from around the world detected an explosion on the surface of SGR 1806-20, a neutron star 50,000 light years away. The resulting flash of energy — which lasted only a tenth of a second — released more energy than the Sun emits in 150,000 years.
Combing through data from NASA’s Rossi X-ray Timing Explorer, a team of astronomers has identified oscillations in the X-ray emission of SGR 1806-20. These rapid fluctuations, which began 3 minutes after the starquake and trailed off 10 minutes later, had a frequency of 94.5 Hertz.
“This is near the frequency of the 22nd key of a piano, F sharp,” said Tomaso Belloni from Italy’s National Institute of Astrophysics.
Just as geologists study the Earth’s interior using seismic waves after an earthquake, astrophysicists can use the X-ray oscillations to probe this distant neutron star.
More here.