Superkilonova

A giant star in a galaxy more than a billion light-years from Earth died a spectacular death. Then it might have died again – an event that was even more spectacular than the first. The double demise earned it a doubly impressive title: a superkilonova – two powerful explosions from a single star.

The system was discovered last August. It produced a huge outburst of gravitational waves – ripples in spacetime. Astronomers first thought it was a kilonova – the violent merger of two super-dense corpses known as neutron stars. Such mergers produce huge amounts of the heaviest elements in the universe, including gold, platinum, and uranium.

After a few days, though, the event began to look more like a type of supernova – the explosion of a star much heavier than the Sun. But as astronomers followed the outburst with a dozen telescopes on the ground, one team suggested that it might have been both.

The supernova came first. The massive star’s core collapsed to make a neutron star. Its outer layers then blasted into space.

But the collapsing core might have split apart to make two neutron stars, not one. Or the second neutron star might have come together from debris around the first one. Either way, the tiny but massive neutron stars quickly spiraled together. That set off the second blast – a kilonova.

There are other possible explanations for the object. But for now, a superkilonova tops the list.

Script by Damond Benningfield