A brilliant cosmic burst 100 times as bright as our galaxy came from 2 black holes circling each other, study finds

• Huge cosmic bursts are coming from two black holes circling each other in a distant galaxy.
• One of these flares was 100 times brighter than our galaxy and only lasted one day. 
• The system consists of a smaller black hole orbiting a larger one at near the speed of light.

In galaxy OJ287, which lives 5 billion light-years away, there was a massive burst of light that shone 100 times brighter than our home galaxy, the Milky Way.

There are few cosmic giants in our universe that can produce such a spectacle. In this case, the flare came from a binary system consisting of two black holes trapped in a rapid dance.

The smaller black hole, with a mass of about 150 million suns, orbits its larger companion, with a mass of 18 billion suns, at near the speed of light.

It's this rapid dance that sparked the bright flare from this system, according to a new study published in Monthly Notices of the Royal Astronomical Society in March.

A cosmic burst 100 times brighter than our galaxy

The recorded burst, which astronomers observed in February 2022, occurred when the smaller black hole crashed into a disk of gas surrounding the larger black hole, the study's scientists said. 

Gaseous discs like this are common because black holes, especially the supermassive ones lurking at the center of galaxies like this one. That's because they have such tremendous gravitational pull, it rips apart stars and other objects that venture too close. The disc of gas, called an accretion disc, is all that remains from the carnage.

As the smaller black hole plunges through the accretion disc at near the speed of light, it swallows up some of that gas, which in turn energizes an explosive jet of radiation that ejects from the smaller black hole. 

"According to the estimates, the flare occurred shortly after the smaller black hole had received a massive dose of new gas to swallow during its plunge," said the study's lead author Mauri Valtonen from the Tata Institute of Fundamental Research, in a statement.

"It is the swallowing process that leads to the sudden brightening of OJ287. It is thought that this process has empowered the jet which shoots out from the smaller black hole of OJ 287," Valtonen added.

A streak of bad luck ended

This is the first time astronomers have observed a flare directly from the smaller black hole in OJ287. That's because the magnificent event only lasted for a day. 

"An event like this was predicted ten years ago, but has not been confirmed until now," Valtonen said in the statement. Adding that, "It turns out that we have simply just had bad luck. Nobody observed OJ287 exactly on those nights when it did its one-night stunt."

The event is the first observational proof that the smaller black hole exists. Up to this point, its presence was only predicted through observations of its gravitational influence on the larger black hole. More specifically, the larger black hole also emits powerful jets of radiation, and these jets have a peculiar wobble that astronomers attribute to the smaller black hole's gravitational influence. 

The black holes are "so close to each other in the sky that one cannot see them separately, they merge to a single point in our telescopes," Valtonen said in the release. 

Valtonen and his team of researchers have seen plenty of other bright flares from this system. In fact, they've been studying the black hole pair for decades, with the first successful campaign dating back to 1983 and follow-up campaigns in 1994, 1995, 2005, 2007, 2015, and 2019.

"The total number of predicted flares now number 26, and nearly all of them have been observed," said co-author of the study Achamveedu Gopakumar from the Tata Institute of Fundamental Research, in the statement. 

These bursts will continue to happen as the smaller black hole orbits the bigger one, although they'll be irregular because the 12-year orbit is oblong, the study said.