Документальный фильм "Superfluids"



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ScienceCasts: Superfluids

The Superfluid Core of a Dead Star — presented by Science at NASA.

Neutron stars are very strange. For one thing, they're made of neutrons, but that's just for starters. A neutron star — the entire star — is smaller than town you live in. Some of them spin around on their axis so fast, they can complete one revolution in less than a millisecond. And a mere teaspoonful of neutron star's solid crust weights more than a billion tons. Very strange indeed. But would you believe, they just got stranger?

Astronomers using NASA's Chandra X-ray Observatory have discovered that neutron stars, one of them at least, has a superfluid core. A superfluid is a bizarre, friction-free state of matter that, here on Earth, exists in laboratories at temperatures near absolute zero. Superfluids have no viscosity, but they do have surface tension. This weird combination causes superfluids to try to climb out of any cup they are placed in, slithering up the sides and over the rim.

Superfluids also have infinite thermal conductivity. They spread heat very rapidly. The thermal character of superfluids is what led to their discovery in a neutron star about 11,000 light years from Earth. The neutron stars is spinning inside a supernova remnant astronomers call "Cassiopeia A" or CAS A for short. Neutron stars are born in supernovas. They are the dead remnant cores of exploded stars. The CAS A explosion happened about 330 years ago (as seen from our planet). That means the neutron star is relatively young and still cooling off from the ferocious blast. It's cooling off so fast in fact, it must have a superfluid inside to help conduct the heat.

That was the conclusion of astronomers who measured the temperature of the star using Chandra and found 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,' says Dany Page of the National Autonomous University in Mexico, who is leading one of two teams studying the phenomenon.

"This means that something unusual is happening within this neutron star." Now, when an astronomer says something "unusual" is happening inside a neutron star, you know it's got to be pretty weird. Page's team and others will continue monitoring the CAS A neutron star, measuring its temperature and spin rate to see if they can learn more about how superfluids behave at high temperature and density. It's the kind of information they could never get from an Earth-bound lab.

Stay tuned to Science@NASA for updates from CAS A and other dead stars around the Milky Way.

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Документальный фильм "Superfluids"

















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