An ultramassive black hole with a mass more than 32.7 billion times our Sun has been discovered in a galaxy cluster known as Abell 1201, located 2.7 billion light-years from Earth. The astronomers’ (astronomers’) new measurement exceeds their previous estimates by at least 7 billion solar masses. It’s one of the largest black holes astronomers have ever detected, approaching sizes that are theoretically thought to be maximum.
Our universe is full of black holes, including supermassive black holes at the centers of galaxies in the space around us. Most of these black holes are inactive, not emitting materials that cause them to glow and make them easier to detect. There are also free black holes wandering in space as they please.
These black holes are much larger than supermassive black holes, such as those found at the center of galaxies. Because they are so large and contain so much mass, you might theoretically expect them to be easier to find. However, the probability of a black hole being found depends on how active it is and how much heat it emits. This is because by their very nature ultramassive black holes (and black holes in general) do not emit light.
This makes black holes very difficult to spot, since the most basic way we can find an object in the dark of space is the light it emits. One of the ways astronomers search for black holes is called gravitational lensing. This method requires astronomers to observe how light moves through a region of space. Looking at ultramassive black holes, light is seen to bend around these holes.
When light approaches a large object in space, it stretches by lensing around it, creating an effect that magnifies and distorts background images. It’s also useful for finding galaxies too far away for us to observe without their enormous magnification capabilities. A group of astronomers first noticed light bending around this ultramassive black hole at the center of Abell 1201 in 2003.
However, this discovery was not further studied until 2017, when astronomers discovered a second blob. More recent simulations have discovered that for light to be bent this way around a black hole, it must have the same mass as about 30 billion Suns, meaning it must be large enough to be an ultramassive black hole.
The researchers involved in the determination reported it on the Monthly Notices of the Royal Astronomical Society. It is hoped this discovery will allow gravitational lensing to look deeper into the universe and discover more ultramassive black holes like this one, which are already among the 10 largest black holes we’ve ever seen detected.
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