The bending of light as it travels around a gigantic invisible mass has revealed the existence of one of the largest black holes discovered in the universe. In the galaxy at the center of a massive cluster called Abell 1201, some 2.7 billion light-years away, a cosmic giant lurks. Not content with being super-large, the beast supermassive A black hole with a mass about 32.7 billion times greater than the mass of the Sun. The new figure shows the power of bent light to accurately measure masses, surpassing previous estimates by at least 7 billion solar masses.

“This particular black hole, about 30 billion times the mass of our sun, is the largest ever discovered and is theoretically at the upper limit of black holes’ reach, so it’s an extremely exciting discovery,” explains the physicist. James Nightingale of Durham University in England.

There are many black holes in the universe, but they are not easy to detect unless there is actively accumulating material – a process that produces large amounts of light as the material heats up before collapsing into a black hole. stain. Black holes themselves don’t emit light that we can detect, so we have to find them by looking at their effect on things around them.

One way to detect these black holes is to look for an effect called gravitational lensing. This happens when space-time itself is distorted by mass; Think of spacetime as a rubber sheet and mass as a heavy weight on it. Any light passing through this region of space-time must follow a curved path, and this may be very interesting to a distant observer.

Light is bent, stretched, and often magnified, meaning we get distorted images of background objects such as distant galaxies. This lensing mass can be as small as a stellar-mass black hole, in which case the phenomenon is called microlensing; or as big as a galaxy cluster. Astronomers can study this distorted light to probe the properties of the lens-forming mass.

The central galaxy or brightest cluster galaxy (BCG) Abell 1201 is a large diffuse elliptical galaxy well known as a strong gravitational lens. A galaxy far beyond BCG appears next to it as a long, eyebrow-like patch that tightly wraps around it. This stain was discovered in 2003; In 2017, astronomers found a second, fainter spot, even closer to the center of the Galaxy.

Astronomers assumed that this meant the presence of a very large black hole at the center of BCG, but the available data were not detailed enough to determine the central mass or provide more information about what was there. Nightingale and her colleagues not only gained access to the latest observations, but also developed tools to make sense of them. They ran hundreds of thousands of simulations of the motion of light in the universe by changing the mass of the black hole at the center of the galaxy, looking for results that replicated the lensing we observed with the Abell 1021 BCG.

All but one of their models supported a massive black hole at the center of the galaxy; and it was 32.7 billion solar masses that best matched the mass of this black hole. This pushes it into the supermassive region, black holes larger than 10 billion Suns, and near the theoretical upper limit of black hole masses of 50 billion Suns. This mass also places the Abell 1021 BCG black hole among the top 10 most massive black holes we’ve discovered to date. The event horizon will cover more than 1290 astronomical units in diameter. For context, Pluto is only 40 AU from the Sun. It’s mind-blowing to think about it.

Abell 1201’s properties as a gravitational lens are quite special, and it’s possible that a detailed measurement of the black hole’s mass in BCG wouldn’t be so obtainable under other conditions, but the Nightingale team is confident their method is reliable. promising. to detect and weigh other black holes in the distant universe.

“Gravitational lensing makes it possible to study inactive black holes, which is currently not possible in distant galaxies,” says Nightingale.

“This approach could allow us to explore many other black holes beyond our local universe and reveal how these exotic objects were transformed into space-time.”