Black holes can be very big, but there is a separate class which is huge and monstrous. Astronomers have identified such a giant black hole whose mass is 40 billion times that of the Sun. It is present at a galaxy’s centre that is known as Holmberg 15A. It is a supergiant elliptical galaxy present at a distance of 700 million light-years away from us that sits at the centre of the galaxy cluster, Abell 85.
This new black hole is one of the largest black holes that have been identified and is the largest among the ones detected by tracking the motion of the stars around it. Past calculations based on the galaxy’s dynamics and its cluster found the mass of Holm 15A*(the black hole) which estimates it to be 310 billion times that of the Sun’s mass. These were indirect measurements of the black hole. The first direct measurement is obtained in this research and the paper has been submitted for peer review to The Astrophysical Journal.
Researchers mentioned in the paper that they used orbit-based, axisymmetric Schwarzschild models for analysing the stellar kinematics of Holm 15A from better resolution, spectral observations obtained with the help of MUSE at VLT. They found a supermassive black hole of mass (4.0 ± 0.80) × 1010 solar masses at Holm 15A’s center. This is the most massive black which has been detected directly in the local Universe.
The black hole with the greatest mass which has been detected so far is quasar TON 618, which weighs nearly 66 billion times the Sun’s mass according to indirect measurements. Event horizon of Holm 15A* which is also called as Schwarzschild radius would be enough to engulf the orbits of all the planets in Solar System and still have space left for some more. Pluto is 39.5 astronomical units from Sun. Heliopause is estimated to be nearly 123 AU. According to the mass of Holm 15A*, the Schwarzschild radius would be 790 AU.
The supermassive black hole of Holm 15A is almost four to nine times bigger than estimated according to stellar velocity and bulge stellar mass of the galaxy. It fits the collision model between two early-type galaxies that have depleted cores. It occurs when there are not many stars present in the core according to the number of stars which are there in the galaxy’s outer regions.
Researchers mentioned that the masses of black holes in cored galaxies such as Holm 15A vary inversely to the mass density and the central stellar surface brightness. They intend to keep studying about the black hole and conduct complex, detailed modelling thereby compare the results with the observations. This can help to understand how often such a merger occurs and how many such black holes remain yet to be discovered.
Journal Reference: arXiv