It must have been quite a bang. The explosion of SGR 1806-20, an ultra-magnetic magnetar, happened quite far away — 50,000 light years from the Earth, in fact — but when the flare hit Earth’s upper atmosphere, it was as though all the Blackpool illuminations were turned on at the same time.
It may have been even brighter, about 10,000 trillion trillion trillion watts, according to the astronomers who noticed something funny in the sky last December. And the explosion must have been deafening: several billion hydrogen bombs going off at once. Krakatoa, by comparison, would have been no more than a gnat’s whisper. Even Ozzy Osbourne in full concert would have been quieter.
Luckily, we do not come across magnetars often. They are so magnetic that they can wipe your credit card clean halfway to the Moon and would play havoc with congestion charging or electronic theatre bookings. In addition, SGR 1806-20 was a soft gamma repeater, and liked to send out lethal gamma ray bursts until, one day, it blew up. In a tenth of a second, it released more energy than the Sun does in 100,000 years. Had it been ten light years away, it would have killed us all.
It is important, in space, to keep a sense of disproportion. Numbers are generally quite large, and what, to us, may seem rather far away is a wafer in time. Several giant meteorites hurtling towards the Earth have missed by just a whisker; one flew between us and the Moon, the equivalent of a daredevil pass under Tower Bridge in a 737 jet. Only now are we discovering the busy lives the stars of the Milky Way led when the dinosaurs walked the Earth. This one went twinkle, twinkle, bang.