Illustration of the stellar merger. Credit: NASA, ESA, and A. Feild.
If the universe were a food, it'd be a bag of microwave popcorn–a violent mess of heat and explosions in every direction. But it's rare when astronomers spy a burst unlike any other before it. Yesterday a team of researchers led by Nial Tanvir of the University of Leicester in the United Kingdom claims they've identified a new kind of pop out there in the cosmos: the kilonova.
In terms of brightness, the kilonova is the middle child of stellar explosions. Although 1000 times brighter than a nova (the glowing pyre of gas devoured by a dead star) it still packs only 1/10 or even 1/100 of the punch of a supernova (the endgame detonation of the galaxy's biggest giants). In a paper published in the science journal Nature yesterday, Tanvir says kilonovas are the radioactive blowback made by a collision of two hyper-dense stars, such as a pair of neutron stars.
The discovery of kilonovas solves part of a longstanding mystery in astrophysics. Periodically, astronomers pick up brief and mysterious blasts of gamma rays. These powerful gamma ray busts last a few seconds at most, and until yesterday their origin was still largely unknown. Although it had been theorized that these bursts were caused by something like the stellar collisions that also cause kilonovas, nobody could be certain because the gamma rays had never been successfully backtracked.
But in June of this year, Tanvir and his team of astronomers were able to follow the trail of a gamma ray burst that lasted just a tenth of a second but was heard by NASA's Swift telescope. The scientists were helped by a prediction by Daniel Kasen, an astrophysicist at the University of California, Berkeley, who was not involved in the study. Kasen had worked on building theoretical models of kilonovas and suggested that they might be obscured in the visible spectrum of light. To find them, he said, "You should really look in the infrared spectrum, which hadn't really been done before."
Tanvir used the Hubble telescope to follow the gamma ray burst in the infrared range of light, and sure enough, caught sight of the glowing, radioactive debris from the neutron star smashup. "It was a challenging observation," Kasen says. "You're trying to chase something that's short lived and very far away."