Super star
15 Mar 2011 by hjcmtbbcwq.d hjcmtbbcwq.d
Scientists studying the remnants of Cassiopeia A – a massive star that exploded 330 years ago – have observed a bizarre state of matter in the core: a superfluid and superconductor.
Scientists studying the remnants of Cassiopeia A – a massive star that exploded 330 years ago – have observed a bizarre state of matter in the core: a superfluid and superconductor.
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Composite of X-rays from Chandra (red, green, and blue) and optical data from Hubble (gold) of Cassiopeia A. Inset: Interior of the neutron star where densities increase from the crust to the core. Credit:NASA/CXC/UNAM/Ioffe/D.Page,P.Shternin et al; NASA/STScI; NASA/CXC/M.Weiss |
Two independent research teams have used data from NASA’s Chandra X-ray observatory to show that the interior of Cassiopeia A (Cas A) – a neutron star – contains superfluid and superconducting matter. Their conclusions have important implications for understanding nuclear interactions in matter at the highest known densities.
A sequence of Chandra observations of the neutron star – the ultra-dense core that remained after the supernova – shows the compact object has cooled by about 4% over the last decade.
“This drop in temperature, although it sounds small, was really dramatic and surprising to see,” said Dany Page, leader of the team from the National Autonomous University. “This means that something unusual is happening within this neutron star.”
Detailed models from theoretical scientists suggest how matter should behave at such high densities, including the formation of superfluids. Superfluids containing charged particles will also be superconductors.
“The rapid cooling in Cas A’s neutron star, seen with Chandra, is the first direct evidence that the cores of these neutron stars are, in fact, made of superfluid and superconducting material,” said Peter Shternin, leader of the second team from the Ioffe Institute, Russia.
The rapid cooling is explained by the formation of a neutron superfluid in the core of the neutron star, suggest both teams. Theory predicts the star should undergo a distinct cool-down during the transition to the superfluid state as neutrinos form and escape the star, taking energy with them.
Superfluidity on Earth occurs at extremely low temperature – near absolute zero – but in neutron stars it can occur at temperatures near a billion degrees. This research confines the critical temperature to between half a billion to just under a billion degrees Celsius.
This research may also be important for understanding a range of behaviour in neutron stars, including glitches and pulsars, neutron star precession and pulsation, magnetar outbursts and the evolution of neutron star magnetic fields.
