The Biggest Splash of Light From Outside the Solar System

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.)