Evidence for a bizarre state of matter was found in the dense core of the star left behind, a so-called neutron star, based on cooling observed in over a decade of Chandra X-Ray Telescope observations. NASA's Chandra X-ray Observatory discovered direct evidence for a superfluid, a strange, friction-free state of matter, at the core of Cassiopeia A.
Superfluids created in laboratories on Earth exhibit remarkable properties, such as the ability to climb upward and escape airtight containers. The discovery has important implications for understanding nuclear interactions in matter at the highest known densities.
Neutron stars contain the densest known matter that is directly observable. One teaspoon of neutron star material weighs six billion tons. The pressure in the star's core is so high that most of the charged particles, electrons and protons, merge resulting in a star composed mostly of uncharged particles called neutrons.
Two independent research teams studied the supernova remnant Cassiopeia A, or Cas A for short, the remains of a massive star 11,000 light years away that would have appeared to explode about 330 years ago as observed from Earth. Chandra data found a rapid decline in the temperature of the ultra-dense neutron star that remained after the supernova, showing that it had cooled by about four percent over a 10-year period.
"This drop in temperature, although it sounds small, was really dramatic and surprising to see," said Dany Page of the National Autonomous University in Mexico. "This means that something unusual is happening within this neutron star."
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