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