Collapse of star captured for the first time

■ Dubbed ‘The Cow’, object flared up, vanished almost as quickly on telescope

Washington, Jan. 13: A mysterious cosmic explosion detected about 200 million light years away may be the exact moment a star collapsed to form a black hole or neutron star, scientists say.

Researchers from Northwestern University in the US are getting closer to understanding the mysteriously bright object that burst in the northern sky this summer.

On June 17, the ATLAS survey’s twin telescopes in Hawaii found a spectacularly bright anomaly 200 million light years away in the Hercules constellation.

Dubbed AT2018cow or “The Cow,” the object quickly flared up, then vanished almost as quickly.

After combining several imaging sources, including hard X-rays and radiowaves, the multiinstitutional team now speculates that the telescopes captured the exact moment a star collapsed to form a compact object, such as a black hole or neutron star.

The stellar debris, approaching and swirling around the object’s event horizon, caused the remarkably bright glow.

This rare event will help astronomers better understand the physics at play within the first moments of the creation of a black hole or neutron star.

“We think that ‘The Cow’ is the formation of an accreting black hole or neutron star,” said Raffaella Margutti, from Northwestern University, who led the research.

“We know from theory that black holes and neutron stars form when a star dies, but we’ve never seen them right after they are born. Never,” Margutti said.

After it was first spotted, The Cow captured immediate international interest and left astronomers scratching their heads.

“We thought it must be a supernova. But what we observed challenged our current notions of stellar death,” Margutti said.

For one, the anomaly was unnaturally bright — 10 to

100 times brighter than a typical supernova. It also flared up and disappeared much faster than other known star explosions, with particles flying at

30,000 km per second (or 10 per cent of the speed of light).

Within just 16 days, the object had already emitted most of its power. In a universe where some phenomena last for millions and billions of years, two weeks amounts to the blink of an eye.

“We knew right away that this source went from inactive to peak luminosity within just a few days,” Margutti said.

We know from theory that black holes and neutron stars form when a star dies, but we’ve never seen them right after they are born. Never — RAFFAELLA MARGUTTI, lead researcher, Northwestern University