The hottest superconductor in the Universe

Southampton researchers have made new discoveries about a remnant of an exploded star, confirming long-held scientific theories for the first time and pushing the boundaries of knowledge about our Universe.

When a massive star runs out of nuclear fuel, it undergoes a supernova explosion and the remains at the stellar centre form either a neutron star or a black hole. Our scientists have been studying the central object in Cassiopeia A, a neutron star that resulted from a supernova whose light reached the Earth over 300 years ago.

Nils Andersson, Head of the University's General Relativity Group, says: "Researchers have always thought that these objects would be superfluid (have no internal friction or viscosity) and superconducting (able to conduct electricity with no loss of energy). We now have clear observational evidence that supports these ideas."

The debris from the Cassiopeia supernova was discovered by British astronomers in the 1940s. However, the compact object at the centre of the supernova was not seen until 1999, when it was detected by NASA's Chandra X-ray Observatory.

Using theoretical models and Chandra observations spanning 10 years, Southampton researchers were instrumental in identifying the object as a neutron star and in measuring its carbon surface composition.

Nils explains: "Follow-up work has shown that the neutron star is cooling in real time. The observed cooling rate provides the first evidence that the star's interior is superfluid and superconducting. These findings are all first-time discoveries in astronomy."

Dr Wynn Ho, lead Southampton researcher on the project, comments: "The age of Cassiopeia A makes it the youngest neutron star in our galaxy and, at a temperature of about one billion degrees, it is the hottest known superfluid and superconductor in the Universe."

"To compare theoretical models with real observations in this field is a big step," adds Nils. "It has enabled us to push the boundaries of our knowledge of the Universe and gain a better understanding of the way matter behaves under extreme conditions."