The explosive collision of neutron stars may have created a rare and extreme star

when two neutron stars collide, the universe leaps. The extreme crash is explosive and creates a “kilonova”, which emits a bright and rapid flash of gamma rays. It also sends ripples through the fabric of space-time. So, scientists believe, the cosmic crash will likely create a newly melted object that will rapidly collapse into a black hole. But … what if he survives?

A new study, to be published in The Astrophysical Journal but available as a preprint on arXiv, describes the brightest kilonova ever seen and suggests that a collision of a neutron star could sometimes give rise to a magnetar, an extreme neutron star with dense magnetic fields.

On May 22, NASA’s Neil Gehrels Swift Observatory, a space telescope, spotted a gamma-ray burst in an extremely distant corner of space, dubbed GRB 200522A. Scientists believe this kind of short bursts occur when two neutron stars collide, so when a telescope sees one, there’s a mad rush to get observations at other wavelengths on the electromagnetic spectrum. The collision in question occurred about 5.5 billion years ago, but only now our telescopes have picked up the signals.

In the new study, the research team pointed to GRB 200522A several space and ground-based telescopes, including NASA’s Hubble Space Telescope, and observed the fallout after the gamma-ray burst of light.

Using X-ray, radio and near-infrared data, the team was able to measure the brightness of the gamma-ray burst. But there was one particular observation that didn’t fit. Near-infrared images from Hubble showed an extremely bright explosion – about 10 times brighter than any kilonova ever seen (although only a handful have been observed so far).

“We scratched our heads for a while and looked at all the possible models at our disposal,” says Wen-fai Fong, an astrophysicist at Northwestern University and lead author of the new research. “The near-infrared light we saw from GRB 200522A was too intense to be explained by a standard radioactively powered kilonova.”

Fong and his team ultimately settled on a model they dubbed “magnetar-enhanced kilonova” to explain the extreme brightness.

Kilonovas are created when two dense cosmic objects, such as neutron stars and black holes, crash into each other. The fusion process ejects a ton of subatomic material into space, including the generation of the gamma-ray burst. Fong says you can think of it as a smoothie in a blender that you forgot to put the lid on, with “neutron-rich” material flowing into the cosmos.

The team’s model suggests that the creation of a magnetar, a highly magnetized type of neutron star, may have been able to overload the kilonova event, making it much brighter than astronomers predicted.

“If confirmed, this would be the first time we could see the birth of a magnetar from a pair of neutron stars,” says Fong.

But there is work to be done. Continuing to observe GRB 200522A with radio telescopes will help to more clearly determine what exactly happened around the gamma-ray burst. The radio waves from the event should be able to confirm what was seen at infrared wavelengths, but the time it takes these waves to reach Earth depends on the environment around GRB 200522A. The model suggests it could take about six years to pick up such a signal, and Fong says the team will monitor radio emissions for years to come.

Magnetars have long been mysterious cosmic bodies, but in the past week, astronomers have begun to shed light on the elusive dead stars. Last week, a team of astrophysicists reported the discovery of a fast radio burst (FRB) from a magnetar inside the Milky Way. The important discovery suggests that magnetars may be able to create these mysterious radio signals at times, although the jury is out on whether they can create all the FRBs. GRB 200522A may provide an opportunity to re-test this hypothesis.

“If we were able to associate an FRB with the location of GRB 200522A, it would be a surprising discovery and it would indeed be a smoking gun that links this particular event to a magnetar,” says Fong. However, he warns that it would be surprising if there was a connection between the short gamma-ray bursts themselves and the FRBs.

But gamma-ray bursts continue to raise new cosmic mysteries and puzzles to solve. “I’ve been studying the same type of explosion for a decade now, and brief gamma-ray bursts can still surprise and amaze me,” notes Fong.