Scientists have discovered supermassive black holes at the hearts of large galaxies, with masses equivalent to millions or billions of suns. Some black holes, called “ultramassive black holes,” exceed even these enormous masses.
The largest known black hole is Phoenix A, located at the center of the Phoenix cluster, 5.8 billion light-years away, with an estimated mass of 100 billion suns. Another massive black hole is Tonantzintla 618 (Ton 618), about a billion light-years away, with a mass of around 66 billion suns.
With ultramassive black holes like Phoenix A and Ton 618, scientists are curious about the limit to how large black holes can get.
A team led by Priyamvada Natarajan from Yale University’s Department of Astronomy believes they have some answers. They define ultramassive black holes as those exceeding 10 billion times the sun’s mass, which is 10,000 times larger than supermassive black holes.
Where to hunt ultramassive black holes?
To study ultramassive black holes, researchers first need to locate them. Natarajan suggests that these colossal black holes are likely found in the brightest galaxies with the most stars, especially the Brightest Central Galaxies (BCGs) at the center of galaxy clusters.
These black holes play a crucial role in the growth and formation of stars in galaxies. Ultramassive black holes can be found in the centers of nearby BCGs, indicating a connection between the brightness of galaxies and the presence of these massive black holes.
Black holes enforce their growth limit by feeding on gas that flows into galaxies’ centers. However, they do not consume all the gas, and the excess is expelled as astrophysical jets, influencing star formation by heating and preventing gas condensation.
This self-regulating mechanism limits the growth of black holes and prevents them from becoming excessively large. Natarajan’s team suggests that the upper limit for ultramassive black holes may be around 100 billion solar masses.
Phoenix A may represent the largest black hole discovered yet, approaching this limit. Natarajan’s team is now shifting focus to intermediate-mass black holes, bridging the gap between supermassive and stellar-mass black holes.
Their research is detailed in a paper on the site arXiv.
