Meet the Kilonova, Your New Favorite Cosmic Explosion

Space is full of high energy explosions, deadly meetings between stars that produce blinding flashes of light and swaths of radiation. But the most badass, at least in name, would have to be the kilonova. It’s a newly discovered type of stellar blast that happens when two compact objects like neutron stars smash into each other, and it’s the smoking gun that finally explains short gamma ray bursts.

Gamma ray bursts are flashes of intense high-energy radiation that reach the Earth from random directions in space. And there are two type: short GRBs that last up to two seconds and long GRBs that last longer than two seconds. We know more about long GRBs; scientists have gathered a fair bit of evidence to suggest that these are produced by the collapse of extremely massive stars.

But explaining the short GRBs has been a different matter. Circumstantial evidence has suggested that these short bursts are the result of two compact objects merging, specifically two neutron stars like those in a binary system spiraling into one another.

Neutron stars are city-sized super dense stellar objects nearly 1.5 times as massive as the Sun. They are born when stars four to eight times as massive as our Sun explode. The outer material shoots off into space while gravity tightly condenses the remaining material into a super dense star remnant. The material is so tightly pressed together that the protons and electrons make neutrons, hence the name “neutron stars.”

It’s possible for two neutron stars to be quite close together, orbiting one another as a binary star system. And as a binary system, the two neutron stars could spiral slowly towards each other making a crash inevitable. In the milliseconds before the two neutron stars collide, both would shoot out highly radioactive material that heats up and expands to emit a burst of light. This is the kilonova, the fireball blocks all visible light but radiates in the infrared end of the electromagnetic spectrum making it possible to image.

This was just a theory until June 3 when scientists found evidence of its validity. NASA' s Swift space telescope picked up the extremely bright gamma ray burst labeled GRB 130603B. The flash, which lasted just one-tenth of a second, was roughly 100 billion times brighter than the resulting kilonova flash.

Scientists spent two days–June 12 and 13–searching for the location of the initial burst. And they finally found a faint red object using the Hubble Space Telescope; it was the kilonova’s glow. Subsequent observations confirmed the source of the flash was in that area but had faded away.

Interestingly, it was the lack of material scientists needed to prove that the infrared glow was in fact the result of two objects merging and the cause behind the short gamma ray burst. Finding something occasionally means finding nothing.