In a First, Astronomers Witnessed the Birth of a Supermassive Magnetar Following a Glorious Kilonova

The scientists originally thought that the cosmic crash would create a black hole

An image of a kilonova in space. There is a bright, purple, circular glow in the middle of the image with two beams of blue light extending diagonally across it. Bright blue "clouds" surround the two beams. The background shows stars twinkling in space.
The spinning magnetar transferred a remarkable amount of energy to the debris created by the collision, heating the material up and generating a bright glow. NASA, ESA and D. Player (STScI)

This year, astronomers witnessed a cosmic spectacle when two neutron stars—the dense remains of collapsing stars—crashed into each other billions of lightyears away. Their gargantuan collision lit up the galaxy with a flash and gave rise to a magnetar—a supermassive star with a hyper-powerful magnetic field. Astronomers have known about magnetars, but this event marks the first time they've ever witnessed one being born, reports Rafi Letzer for Live Science.

Using remarkably powerful equipment, including the Hubble Space Telescope and the Swift Observatory, the scientists observed a quick flash of light on May 22. The stars' collision certainly didn't occur that night—instead, it occurred 5.47 billion years ago, and its light had just reached Earth, according to a press release.

The team observed a quick flash of gamma radiation, the result of the stars crashing and sending space matter blasting through the galaxy to settle among the stars. Then came the long-burning glow of a kilonova—a colossal explosion that produces heavy elements like gold and platinum—as the space dust swirled around the newly formed magnetar, reports Live Science.

The explosion released more energy in half a second than the sun emits over ten billion years, according to another press release.

But the scientists noticed something even more bewildering: The flash emitted ten times the average amount of infrared light, reports Meghan Bartels for Space.com. The findings will be published in The Astrophysical Journal and are currently available on the pre-print server arXiv.org.

"When two neutron stars merge, the most common predicted outcome is that they form a heavy neutron star that collapses into a black hole within milliseconds or less," lead author Wen-fai Fong, an astrophysicist at Northwestern University, says in a press release.

"Our study shows that it’s possible that, for this particular short gamma-ray burst, the heavy object survived," Fong says. "Instead of collapsing into a black hole, it became a magnetar: A rapidly spinning neutron star that has large magnetic fields, dumping energy into its surrounding environment and creating the very bright glow that we see."

The spinning magnetar transferred a remarkable amount of energy to the debris created by the collision, heating the material up and generating a bright glow, Richard A. Lovett for Cosmos.

"I’ve been studying these short gamma-ray bursts for a decade now," Fong tells Cosmos. "Just when you think you understood them, they throw a new twist at you. The Universe produces such a diversity of explosions."