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Slowing Down

September 20, 2013

In the spring of 2012, a spinning stellar corpse suddenly slammed on the brakes. In an instant, its rotation rate slowed by about two millionths of a second. That may not sound like much until you consider this: the dead star was spinning once every seven seconds, and it weighs a half-million times more than the entire planet Earth. So slowing it down would take some pretty good brakes.

This object is a neutron star — the crushed core of a once-mighty star that exploded as a supernova. Despite its great heft, it’s only about a dozen miles in diameter.

Astronomers have watched the neutron star for years with X-ray telescopes in space. A couple of times, the star’s rotation rate has actually sped up — something that happens to quite a few neutron stars. But for the most part, it maintained a steady cycle, spinning about eight times a minute.

In April of last year, though, it produced a short but intense burst of X-rays. When astronomers looked at it afterwards, it had slowed down — something that no neutron star had ever been seen to do before.

The brake could have been the star’s interior. A neutron star consists of a solid crust, with a bizarre “fluid” beneath it. As the star spins, these two layers can rotate at different speeds. It’s possible that in this case, the fluid layer was spinning slower than the crust, and it “grabbed” the crust and slowed it down. That could have triggered the outburst of X-rays — and put the brakes on this tiny dead star.


Script by Damond Benningfield, Copyright 2013

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