Exactly how powerful is a magnetar?

Mousetrap

On Dec. 27, 2004, nearly fourteen years ago, the Earth was rocked by a cosmic blast so epic its scale is nearly impossible to exaggerate.The flood of gamma and X-rays that washed over the Earth was detected by several satellites designed to observe the high-energy skies.

Astronomers identified what this was, though they could scarcely believe it. It was caused by the magnetar SGR 1806-20.

Magnetars are neutron stars, the incredibly dense remnants of a supernovae explosions. They can have masses up to twice that of the Sun, but are so compact they may be less than 20 kilometers (12 miles) across.The surface gravity of a neutron star is therefore unimaginably strong, tens or even hundreds of billion times that of the Earth.

What happened that fateful day on SGR 1806-20 was most likely a star quake, a crack in the crust. This shook the magnetic field of the star violently, and caused an eruption of energy. The sheer amount energy generated is difficult to comprehend. Although the crust probably shifted by only a centimeter, the incredible density and gravity made that a violent event far beyond anything we mere humans have experienced. The quake itself would have registered as 23 on the Richter scale. The largest earthquake ever recorded was about 9 on that scale, and it’s a logarithmic scale.

The blast of energy surged away from the magnetar, out into the galaxy. In just 200 milliseconds—a fifth of a second, literally the blink of an eye—the eruption gave off as much energy as the Sun does in a quarter of a million years. And by the way, did you know that the magnetar is 50,000 light years away? That’s 500 quadrillion kilometers (300 quadrillion miles) away, about halfway across the Milky Way galaxy itself!

To read the whole article: http://www.slate.com/blogs/bad_a ... cember_27_2004.html

Chang Tikhak

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