Artist conception of the December 27, 2004 gamma ray flare expanding from SGR 1806-20 and impacting Earth’s atmosphere. Credit: NASA
An artist conception of the SGR 1806-20 magnetar including magnetic field lines.
Credit: NASA
In this weeks Nature, there's a series of articles on the giant flash of Dec 27, 2004: Nature article
This was a truly mind-boggling event. It was so powerful that it bounced off the Moon and lit up the Earth's upper atmosphere. The flash was brighter than anything ever detected from beyond our Solar System and lasted over a tenth of a second. Two similar flares had previously been detected from different sources during 30 years of observations. But it outshone both the preceding events by two orders of magnitude, releasing in its first fraction of a second as much energy as the Sun releases in a quarter of a million years.
SGR stands for soft gamma repeater, because they flare up randomly and release gamma rays.
A strange coincidence in timing has been noted (see this site, for example) - the Sumatra earthquake and tsunami occured the day before, December 26, 2004. Hmmm, maybe gravity waves, whatever, the day before that was Christmas, can't forget that either.
Link to a NASA article on the flash
