Neutron Stars Smash Together, forging gold in an explosive Kilonova

The gravitational wave laser interferometer (LIGO) observatory famously detects gravitational waves by observing black hole collisions. It also addresses collisions of other cosmic bodies, such as when detecting the first fusion observed between two neutron stars in 2017. A team of astronomers examined older data to observe what is happening during these epic impacts.

When two neutron stars collide, the impact creates an explosion – not a supernova, as is the case when a star dies, but a kilonova. The fusion of neutron stars produces massive bursts of gamma rays and electromagnetic radiation, but the process is not purely destructive. He also creates, forging heavy metals such as platinum and gold. In fact, a kilonova at one time forms several heavy metals worth several planets, and it is believed that this is how gold on Earth was created.

Since the scientists observed the neutron star fusion in 2017, they have learned more about what a kilonova would like to see us here on Earth. And this allowed them to go back to older data and locate the previous kilonovae. A burst of gamma rays was observed in August 2016, named GRB160821B, and a recent review of the data showed that a kilonova until then misunderstood was actually produced.

"The 2016 event was very exciting at first," said Eleonora Troja, lead author of the study, in a statement. "It was close and visible with all the big telescopes, including NASA's Hubble Space Telescope. But that does not correspond to our forecasts: we expected that the infrared emission becomes more and more brilliant over several weeks. "

But that's not what happened. "Ten days after the event, there was almost no signal left," continued Troja. "We were all disappointed. Then, a year later, the LIGO event is produced. We examined our old data with new eyes and we realized that we had caught a kilonova in 2016. It was an almost perfect match. The infrared data for both events has similar brightness and an identical time scale. "

As the 2016 event data closely resemble those of the 2017 event, researchers are relatively certain that the 2016 event was also due to the fusion of two neutron stars. There are other ways to generate a kilonova, such as the fusion of a black hole and a neutron star, but scientists believe that this would likely generate different observations in terms of signal signals. X-ray, infrared, radio and optical.

The results are published in the Monthly Notices journal of the Royal Astronomical Society.

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