On February 11, astronomers saw a distant flash of light that seemed to come from a source as bright as a quadrillion suns. They alerted other scientists to the event, and several telescopes quickly pivoted to focus on the flash. Now, two teams of researchers have identified its source: a black hole feasting in the distant universe.
Black holes are famously dark; their gravitational pull is so strong that even light cannot escape their event horizons. In this case, the bright flash was caused by how energetically the black hole consumed its meal, a star that had passed too close to the ravenous compact object. Details of this luminous feast were published today in papers in Nature and Nature Astronomy.
“This particular event was 100 times more powerful than the most powerful gamma-ray burst afterglow,” said Dheeraj Pasham, an astrophysicist at MIT and lead author of the Nature Astronomy paper, in a press release. “It was something extraordinary.”
Every so often, an unlucky star is caught up in the inescapable gravity of a black hole. The spinning black hole tears the star limb from metaphorical limb, until the star’s material is just a superheated swirl around the black hole. These feedings can give off lots of light. AT 2022cmc is the brightest and most distant tidal disruption event yet-known; its source is a supermassive black hole about 8.5 billion light-years away.
Tidal disruption events are useful for astrophysicists; they can reveal how fast black holes are spinning and the rate at which the behemoth objects are feeding. They also can reveal how supermassive black holes grow and shape the galaxies that ensconce them.
Sometimes — and astronomers think they might now know exactly how often — the black hole spews superheated jets of material out into space. The energised jets are accelerated to nearly the speed of light and can be very difficult to see unless they’re pointed directly at us. Which was the case for 2022cmc.
Because the black hole’s jet is pointed at Earth, it appears much brighter to us than it would otherwise. That helped the two research teams observe the light source, despite its extraordinary distance.
Twenty-one telescopes around the world viewed the jet in the X-ray, radio, optical, and ultraviolet wavelengths. It’s the first time a jetted tidal disruption event has been seen at optical wavelengths, the region of the electromagnetic spectrum that the human eye can see.
The X-ray emissions fluctuated dramatically over the course of the observations. The researchers suspect this may be due to a period in which the black hole accreted (i.e. collected) a ton of material around itself.
Comparing the light from this event to other luminous happenings in the cosmos, the teams determined that a jetted tidal disruption event was the sole possible culprit.
“The universe is truly full of surprises and we have to be ready to catch them,” Andreoni said. “Developing more tools and new technology is surely a pathway to discovery, but also persistence and really the wish to be thrilled by the sky at any time when we least expect it.”
Pasham added that other sky surveys could reveal more tidal disruptions in the future, which could then be scrutinised by space-based observatories like the Webb Telescope.
Tools like the LSST Camera — which will be the world’s largest digital camera when it’s mounted at the Rubin observatory in Chile — will be a remarkable resource for regularly imaging the night sky and all the dynamic events in it.
More: Behold: The First Image of Our Galaxy’s Central Black Hole