What a Blast!

Think quickly: Where were you on August 27? That, according to NASA scientists, is when the biggest Earth-bound burst of gamma rays and X rays ever recorded pummeled our planet's upper atmosphere, disrupting radio broadcasts and satellite transmissions -- whilst the occupants, safely sheltered beneath a thick blanket of air, remained largely oblivious. The source of this blistering radiation: a tiny star, measuring a mere 12 miles in diameter (roughly the size of Washington, D.C.), speeding more than 20,000 light-years away on the other side of the Milky Way.

Small and distant though it may be, this star is no ball of gas. It's a solid chunk of nuclear material known as a magnetar -- the existence of which has never been proved before. "These things were only predicted six years ago," says TIME senior science writer Michael Lemonick. "The predictions weren't taken seriously at first; it just didn't make sense." In fact, what physicists scoffed at turns out to be one of the most energetic objects in the universe -- a form of neutron star left over from a supernova, so tightly packed that its magnetic field is a trillion times stronger than the sun's. If we could have harnessed that single wave of energy, it would have been enough to "power all of human civilization on Earth for a billion billion years," according to Kevin Hurley of the University of California at Berkeley. "I've never seen anything like it." Most of us never saw it at all.