Credit: NASA/SAO/CXC/P.Slane et al.

Neutron Star Misnomer?

Neutron stars, the remains of an exploded star, are some of the densest objects in the Universe. As their name suggests, these objects are thought to be composed entirely of neutrons. But since we don't know precisely how matter behaves at such extreme densities, astronomers don't really know what types of matter actually makes up these stars. The density of an object is a measure of its composition, but, while astronomers can (in many cases) determine the masses of neutron stars quite accurately, it's very difficult to measure the size of these stars very accurately, so the densities of neutron stars are generally not known. The difficulty of determining the size of these stars means that astronomers must use other methods to infer compositions. Because these stars must be born hot, and the way they cool depends on their composition, by measuring the temperature of a neutron star, astronomers can infer its composition. Using the spectral and spatial resolution of the Chandra X-ray telescope, astronomers have for the first time measured an accurate temperature of the neutron star embedded in the supernova remnant 3C58, the remains of a star which exploded in A. D. 1181. The temperature derived from these X-ray observations is less than 1 million degrees, much cooler than expected if the star is composed of pure neutrons. This suggests that this neutron star is not composed entirely of neutrons, as expected, and that newer, stranger forms of matter may be required.

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Page Author: Dr. Michael F. Corcoran
Last modified April 15, 2002