Last week, NASA scientist Dany Page, working in tandem with astronomers from all over North America discovered the first evidence for the existence of superfluids in nature. The Chandra X-ray observatory observed the remnants of a 330-year old supernova from the star Cassiopeia A, or Cas A, with important results for science.
Superfluids are an alternate state of matter with extraordinary properties: zero viscosity, zero entropy, and perfect thermal conductivity. This means that, while known superfluids may look like a liquid, they spread out on any surface they touch without restriction — including up and over walls. They do this by overcoming the forces of friction and gravity. No matter how far a superfluid spreads out, the temperature within the entire fluid remains perfectly even across the substance without energy loss.
The property of theoretical zero viscosity leading to superfluids was first hypothesised by John Allen, Don Misener, and Pyotr Kapitsa in 1937. However, only the direct observations of this state of matter earned a Nobel Prize for L.D. Landau in 1962. On Earth, superfluids never occur in nature and can only be produced artificially under extreme conditions, with laboratory temperatures reaching near absolute zero, or -273.15 degrees celcius.
Canadian astronomer Craig Heinke at the University of Alberta, and British astronomer Wynn Ho, found that the neutron star resulting from the supernova Cas A is experiencing a rapid decline in temperature. A neutron star, often the final outcome of such supernovas, is a ball of hyper-dense matter. It is formed from neutrons being compacted as closely as possible, and is so dense that just a teaspoon of it would weigh more than a billion tons. In this extremely dense, heavy star, scientists could not account for the rapid decline in temperature using a normal explanation.
Instead, on February 25, Page and colleagues proposed in Physical Review Letters that this decline is best understood by the formation of a neutron superfluid at the very core of the star. This is possible because the intense pressure and gravity at the heart of the super-dense neutron star raises the critical point of this state of matter from absolute zero to nearly one billion degrees.
Cas A offers a rare chance for scientists to observe not only the natural occurrence of superfluids, but a new type of superfluid. Since Cas A is so young, it may help identify the formation of these unique stellar objects and some of their properties. Specifically, astronomers suspect that there is a relationship between this superfluid core, “glitches” (sudden increases in rotation speed), pulsation, energy outbursts, and neutron stars’ magnetic fields.
