Read this from the Bad Astronomer:

http://blogs.discovermagazine.com/badastronomy/2009/06/18/ok-so-maybe-we-can-be-a-little-frightened/

To quote:

"In December 2004, the magnetar SGR 1806-20 underwent such a starquake. In one-tenth of a second the subsequent blast released something like 2 times 1046 ergs of energy — equal to about 50 trillion times the Sun’s output during that same period.

Holy crap.

This star sits about 50,000 light years from the Earth: literally halfway across the Milky Way galaxy from us. Yet, even from that forbidding distance, this titanic event was able to physically affect the Earth. It compressed our magnetic field and partially ionized our atmosphere, causing it to puff up measurably.

Mind you, it was 500 quadrillion kilometers (300 quadrillion miles) from us at the time."

And astronomers just found a magnetar that is 15,000 light years from Earth.