From the Physics News Update:

THE BIGGEST SPLASH OF LIGHT FROM OUTSIDE THE SOLAR SYSTEM to be
recorded here at Earth occurred on December 27, 2004. The light
came from an object called SGR 1806-20, about 50,000 light years
away in our own galaxy. SGR stands for "soft gamma repeater," a
class of neutron star possessing a gigantic magnetic field. Such
"magnetars" can erupt violently, sending out immense bolts of energy
in the form of light at gamma rays and other wavelength regions of
the electromagnetic spectrum. The eruption was first seen with
orbiting telescopes at the upper end of the spectrum over a period
of minutes and then by more and more telescopes; at radio
wavelengths emissions were monitored for months. For an instant the
flare was brighter than the full moon. (NASA press conference, 18
February; www.nrao.edu/pr/2005/sgrburst/;
www.ras.org.uk/html/press/pn0505ras.html; many telescopes
participated in the observations and results will appear in a
forthcoming issue of Nature.)