XMM Image of wobbling Neutron star
Credit:F. Haberl & ESA

Wobble of the Dead

Neutron stars are one of the endpoints of stellar evolution. They are the tiny remains of the ultradense cores of very massive stars which have exploded. They are born small and hot, but how small, how hot, and how fast they cool down, has largely remained a mystery. One of the best ways to take a young neutron star's temperature is by measuring its X-ray spectrum. And once the temperature is determined, scientists can use the temperature and brightness to figure out how large the neutron star is, to compare that number with theoretical predictions. A recent observation of an isolated, hot neutron star obtained by the XMM-Newton X-ray observatory has allowed astronomers to take its X-ray temperature. Or temperatures, since the star surprised astronomers by having more than one. The XMM-Newton X-ray spectra shows that the star changes from a cool state to a hotter one and back. Astronomers don't believe this represents a real change in the temperature of the neutron star - rather it suggests that the surface of the star is not at a uniform temperature. The apparent change in temperature is thought to be due to a wobble in the spin of the neutron star; the wobble makes the hot region face astronomers sometimes, and sometimes the cooler region.

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Page Author: Dr. Michael F. Corcoran
Last modified Friday, 20-Apr-2012 15:20:51 EDT