Black holes are growing faster than the previous suggestions

Star cluster and black hole (Credit: Gabriel Perez Diaz /Swinburne University)

Astronomers have found that the black holes are growing at a faster rate than previous proposals.

This has been published in The Astrophysical Journal.

Scientists were of the view that the mass of the supermassive black holes increase in close association with the growth of their host galaxy but this new research has presented something totally different.

“Black holes have been growing much faster than we thought,” Professor Alister Graham from Swinburne’s Centre for Astrophysics and Supercomputing said.

New stars (for their formation) and the central black hole (for feeding) compete with each other for the available gas within galaxies. For more than ten years, scientists believe that a fixed amount of gas is distributed between these processes efficiently sustaining the ratio of black hole mass to galaxy mass. However, according to new research, done with the Hubble Space Telescope, the European Very Large Telescope in Chile and the Keck Telescope in Hawaii this, present belief has to be changed.

“We now know that each ten-fold increase of a galaxy’s stellar mass is associated with a much larger 100-fold increase in its black hole mass,” Professor Graham said. “This has widespread implications for our understanding of galaxy and black hole coevolution.”

Moreover, scientists have also observed the opposite behavior the tightly packed cluster of stars at the centers of the galaxies and the disk galaxies.

“The smaller the galaxy, the greater the fraction of stars in these dense, compact clusters,” Swinburne researcher Dr Nicholas Scott said. “In the lower mass galaxies the star clusters, which can contain up to millions of stars, really dominate over the black holes.”

This research has also pointed to the presence of “intermediate mass” black holes in numerous galaxies known to have black holes. “Intermediate mass” black holes are the objects having masses between that of a single star and one million stars. According to Professor Graham, these black holes are so big that they can eat up any stars and their planets.

“These may be big enough to be seen by the new generation of extremely large telescopes,” Dr Scott said.

“Black holes are effectively gravitational prisons and compactors, and this may have been the fate of many past solar systems,” Professor Graham said. “Indeed, such a cosmic dance will contribute at some level to the transformation of nuclear star clusters into massive black holes.”

You can see a short animation of stellar capture by a massive black hole on YouTube at http://astronomy.swin.edu.au/BH

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