Back in late March, NASA's Swift satellite detected a strange and unusual energy explosion in the constellation Draco. NASA now knows what it was: "the awakening of a distant galaxy's dormant black hole as it shredded and consumed a star."

This simulation shows how it works:

As a star falls toward a black hole, it is ripped apart by intense tides. The gas is corralled into a disk that swirls around the black hole and becomes rapidly heated to temperatures of millions of degrees.

The innermost gas in the disk spirals toward the black hole, where rapid motion and magnetism creates dual, oppositely directed "funnels" through which some particles may escape. Particle jets driving matter at velocities greater than 80-90 percent the speed of light form along the black hole's spin axis. In the case of Swift J1644+57, one of these jets happened to point straight at Earth.

According to the researchers, the black hole may be "twice the mass of the four-million-solar-mass black hole lurking at the center of our own Milky Way galaxy". [NASA Goddard]