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A star’s spin opens an exotic window for McGill University researcher

Astrophysicist Victoria Kaspi of McGill University poses in her home, in Montreal, June 5, 2007.

Christinne Muschi/The Globe and Mail

There's a new phenomenon in the universe and Vicky Kaspi calls it the "anti-glitch."

Dr. Kaspi is an expert in observing neutron stars – small, but mind-bogglingly dense objects that are created whenever a dying giant star collapses in on itself and squishes the mass of a couple of suns into an object the size of a city. Just a thimbleful of neutron star stuff would weigh about a billion tonnes. Add to this the fact that they spin at breakneck speeds and have magnetic fields strong enough to wipe out a credit card at the distance of the moon and you've got scientists' attention.

"It really is the physics of the extreme," said Dr. Kaspi, who is based at McGill University in Montreal. "These are conditions you can't even hope to simulate in a laboratory."

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Motivated by the promise that neutron stars can shed light on the fundamental nature of matter, Dr. Kaspi and her team have been patiently spying on a number of them, waiting for something interesting to happen.

Now something has.

Dr. Kaspi's latest data show that back in April, 2012, a neutron star that goes by the prosaic name 1E 2259+586 suddenly started spinning more slowly. The difference was slight, only about two millionths of a second off of its usual rotation rate, but it's a behaviour that hasn't been observed until now.

In the past, many neutron stars have been known to occasionally speed up as they spin – a change that's known as a "glitch" because astronomers initially thought they were looking at nothing more than glitches in their equipment when they saw them. Dr. Kaspi's discovery marks the first time the opposite change has been seen – the first anti-glitch. She reported her find in this week's edition of the journal Nature and will discuss its implications at the annual meeting of the Canadian Astronomical Society in Vancouver on Thursday.

While there is a theory for glitches, anti-glitches have only tantalizing possibilities. The most interesting among those involve changes within the neutron star's mysterious interior, thought to be a bizarre type of nuclear fluid that flows without friction beneath a white hot crust of solid crystalline iron. The explanation also likely involves magnetism. As it happens, 1E 2259+586 is not just an ordinary neutron star but a very highly magnetized one, known as a magnetar.

Researchers are keen on the find because it will provide a new way to test ideas about what is going on inside this type of neutron star, and potentially deepen our understanding of the forces that underpin everything else in the universe. "That's the beauty of these objects," said Chris Thompson of the Canadian Institute for Theoretical Astrophysics. Dr. Thompson has spent much of his career imaging the inner world of the neutron star – a pursuit that has engaged some of the brightest minds of the past century, including U.S. physicists Richard Feynman and Robert Oppenheimer, father of the atom bomb.

"We have a long way to go before we gain a fully reliable understanding, but the process is challenging and fun," said Robert Duncan, an astrophysicist at the University of Texas at Austin who has already been studying Dr. Kaspi's data.

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Neil Gehrels, who leads NASA's Swift mission – the orbiting spacecraft used to make the find – notes the discovery emerged only because of Dr. Kaspi's continuing effort to keep track of neutron stars, part of a process he calls "adventure astronomy" because it often yields unexpected results.

Dr. Kaspi agrees the anti-glitch could have easily escaped notice without such an effort. "If you're not monitoring these things systematically you miss a whole lot of interesting activity." She is now working with U.S. colleagues on a plan to observe neutron stars on a more continuous basis from the International Space Station.

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