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In a First, a Highly Energetic Neutron Star Was Observed Suddenly Slowing Down

Astronomers are surprised to have observed a neutron star do something they'd never been seen to do before: slow down.
Artist's rendering of an x-ray outburst from a magnetar, via NASA's Goddard Space Flight Center

Cosmically speaking, neutron stars are truly gnarly—the remnants of massive stars gone supernova, they can spin more than 40,000 times a minute, regularly emit massive x-ray blasts, and are so dense that, according to NASA, a teaspoonful of neutron star material would weigh a billion tons here on Earth. In fact, they're so superlative-laden, astronomers are surprised to have observed a neutron star do something they'd never been seen to do before: suddenly slow down.

New research from a multinational team using NASA's Swift x-ray telescope shares observations of the star known simply as 1E 2259+586, which is located about 10,000 light-years away in the direction of Cassiopeia. According to the paper, the star in question is a magnetar, whose powerful magnetic fields (think 5,000 trillion times more powerful than Earth's) are thought to be the source of massive x-ray outbursts.

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"Magnetars are the universe's strongest magnets and are some of the best laboratories we have for understanding pure physics," co-author Jamie Kennea of Penn State said in a release. "The extreme conditions on these stars could never be replicated in any laboratory here on Earth."

1E 2259+586 is the bright blue-white spot in this false-color x-ray image of the remnant of the supernova the star is born of. Credit: ESA/XMM-Newton/M. Sasaki et al.

Aside from the fact that they're massive x-ray outbursts, these projections are notable because they're thought to be caused by rifts between a neutron star's fast-spinning superfluid interior and its crust made of electrons and ions. According to NASA, high-energy streams of particles shooting off a neutron star's surface suck energy from the star's crust, slowing its rotation. The interior, however, keeps spinning, which eventually rips a crack in the crust that allows x-rays to explode out. The event also gives a "kick," known as a glitch, that accelerates the star crust's spin.

Glitches—near-simultaneous x-ray bursts and star acceleration—have been observed before, but a sudden slowdown hasn't. From July 2011 through mid-April 2012, the team observed that the star was gradually slowing its rotation. But in late April, 1E 2259+586 "showed an apparently instantaneous change," a rapid spin down unlike what had been previously observed. The research team calls it an "anti-glitch."

"It affected the magnetar in exactly the opposite manner of every other clearly identified glitch seen in neutron stars,"  said co-author Neil Gehrels, principal investigator of the Swift mission at Goddard Space Flight Center.

As of now, it's not clear if the anti-glitch observed fits the current model of neutron stars' inner workings. As the team writes in its paper, "This event, if of origin internal to the star, is unpredicted in models of neutron star spin-down and is suggestive of differential rotation in the neutron star, further supporting the need for a rethinking of glitch theory for all neutron stars."

If anything, the research shows just how otherworldly chaotic the cosmos can be. It's not the first time a neutron star was observed doing something totally weird, either. One of my personal favorites was the time a neutron star was observed being belched on by a larger neighbor. There was also the time evidence of gamma ray bursts from neutron stars was found in Japanese trees. But suddenly putting on the brakes? That might be the weirdest neutron star observation yet.

@derektmead