Ultramassive black holes, defined as cosmic entities surpassing 10 billion solar masses, may have an upper limit, according to a study led by Dr Priyamvada Natarajan from Yale University’s Department of Astronomy. Published findings indicate that black holes like Phoenix A, with an estimated mass of 100 billion suns, could represent the maximum size achievable by such entities. The study focuses on understanding growth constraints imposed by black holes themselves through self-regulating feedback mechanisms.

Observing Ultramassive Black Holes

It was noted by Dr Natarajan in an interview with Space.com that ultramassive black holes are commonly located within the brightest central galaxies of galaxy clusters. These galaxies, known as Brightest Central Galaxies (BCGs), are theorised to host the most massive black holes due to their high stellar masses. Black holes such as Phoenix A and Tonantzintla 618 (Ton 618), which weigh around 66 billion solar masses, exemplify this theory, according to research insights.

The Mechanism Limiting Growth

Reports suggest that black holes regulate their own growth by ejecting gas through powerful jets, known as astrophysical outflows. These jets, extending tens of light-years, heat surrounding gas and prevent it from condensing into stars, thereby disrupting star formation. This process simultaneously cuts off the gas supply required for the black hole’s further growth. Dr Natarajan explained this phenomenon, emphasising how inefficient accretion and expelled material act as a natural cap on black hole size.

Future Research Directions

Dr Natarajan and her team are now turning their attention to intermediate-mass black holes, described as having masses between stellar-mass and supermassive black holes, as per reports. These objects, which range between 1,000 and 10,000 solar masses, are being investigated as they remain an elusive and less-understood category. The findings aim to provide a clearer picture of black hole evolution across all mass scales.

The study sheds light on the intricate processes governing black hole growth, with 100 billion solar masses emerging as the theoretical ceiling for ultramassive black holes.