Life and Times... Blah Blah: Space: Who Knew, #17

Monday, February 23, 2009

Space: Who Knew, #17

Magnetar

While the name might bear resemblance to an axe-wielding ork, I assure you we're not talking World of Warcraft here. Today's ramble is on a type of star called the Magnetar, thus named after its prominent magnetic field. Check it out:

http://blog.wired.com/wiredscience/2008/06/scientists-find.html

Of the 400 billion stars in our galaxy, only 12 are magnetars -- neutron stars possessed of a magnetic field a quadrillion times stronger than Earth's.

Make that 13. In an article published last Friday in Nature, researchers at NASA's Spitzer Science Space Center describe a newly-found magnetar called SGR 1900+14.

How big is a quadrillion, you ask? It's a million times a billion. As in, 1,000,000,000,000,000. Apply it to magnetic fields, and -- in the well-chosen words of this press release -- you get "extreme fields [that] stretch the very fabric of matter, contorting atoms into thin cigar-shaped structures."

Under that stress, the star's very crust can split open, temporarily releasing "over a thousand times more energy than all of the stars in a galaxy." That appears to have happened around SGR 1900+14; the break in the interstellar dust ring surrounding the star was likely caused by the flare shooting into space.

It appears that the theory of a Magnetar was first established in 1992. Here's another good article, this one from 1998:
http://science.nasa.gov/newhome/headlines/ast20may98_1.htm

On March 5, 1979, gamma ray detectors on nine spacecraft across our solar system recorded an intense radiation spike. It was just 2/10th of a second long - with as much energy as the sun releases in 1,000 years - followed by a 200-second emission that showed a clear 8-second pulsation period (most SGR bursts release as much energy as the sun releases in one year). The position tied the burst to a supernova remnant known as N49 in the Large Magellanic Cloud.

...

"We found that the pulsar was slowing down at a rate that suggested a magnetic field strength of about 800 trillion Gauss, a field strength similar to that for so called magnetars predicted by previous theoretical work," said Kouveliotou.
By comparison, Earth's magnetic field is a mere 0.6 Gauss at the poles, and the best we can sustain in laboratories on the ground is 1 million Gauss - and that's in a small volume. Normal radio pulsars reach about 1 trillion to 5 trillion Gauss, strong but still short of a magnetar.

"If the field really is this strong," notes Kouveliotou, "then magnetism itself can keep the star hot - about 10 million degrees C (18 million deg. F) at the surface - and power the X-rays coming from its rotating surface."