A Journey Through the Universe by New Scientist

Author:New Scientist
Language: eng
Format: epub
Publisher: Quercus
Published: 2018-02-20T16:00:00+00:00

Starquake

The crust of neutron stars is not so highly compressed. It may be more like familiar solid matter, with nuclei and electrons. This stuff is still ultra-strong, but it can be torn apart by the magnetic field of certain neutron stars known as magnetars. Their fields are so strong that if one passed halfway between Earth and the moon, it would wipe the data off every swipe card on Earth. It’s thought that as the fields inside a magnetar twist around they can rip the crust open, releasing a fireball of particles and radiation that astronomers observe as a bright flash of high-energy photons. This is a starquake.

Back in 2006, astronomers used a particularly powerful starquake to measure the thickness of a neutron star crust. It was picked up by NASA’s Rossi X-ray Timing Explorer in December 2004, from a star called SGR 1806-20. A team led by Tod Strohmayer of NASA’s Goddard Space Flight Center found that the quake set the neutron star ringing, with oscillations of various frequencies appearing in the X-ray spectrum. The team think that some waves were ringing through the crust vertically, letting them calculate its thickness: about 1.5 kilometres.

Magnetars may also explain some super-bright supernovae, as their whirling magnetic fields could pump extra energy into the cloud of debris thrown out by an initial supernova explosion that formed the magnetar.

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