A star can “die” more than once. And the second death can be just as impressive as the first. It can produce a brief outburst that’s easily visible across billions of light-years of space.

Such an outburst was detected three years ago in Corona Borealis, the northern crown. The constellation is in the east as night falls at this time of year, and crowns the sky a few hours later.

A space telescope detected a gamma-ray burst — a flash of the most powerful form of energy. For a couple of seconds, it appeared brighter than any other single object in the universe. But follow-up observations from space and the ground saw nothing — no exploding star or anything else that might have produced the gamma rays.

The brightness and brevity of the blast, and the lack of a visible counterpart, suggested a source: the merger of two dead stars — either two neutron stars, or a neutron star and a black hole. Both kinds of objects form when a massive star explodes as a supernova, crushing its now-dead core. Such objects are no more than a few miles across, but several times as massive as the Sun.

When the two dead stars in Corona Borealis collided, they produced a brief but brilliant burst of gamma rays. The rays were “beamed” into space in narrow jets. We saw the outburst only because one of the jets happened to beam in our direction. If it hadn’t, we wouldn’t have seen anything — and the “re-death” of these two stellar corpses would have remained hidden.

Script by Damond Benningfield