Maynooth University Researchers Uncover Mystery of Super-Massive Black Hole Formation

The discovery by the university’s Black Hole Formation research group, featured in scientific journal Nature Astronomy, relates to how smaller black holes grew into super-massive black holes quickly after the Big Bang which birthed the ever-expanding universe we live in. PhD candidate in MU’s Department of Physics, Daxal Mehta, led the research, and he said that the significance of the team’s conclusions provides a “missing link” between the earliest stars and super-massive black holes. “We found that the chaotic conditions that existed in the early Universe triggered early, smaller black holes to grow into the super-massive black holes we see later following a feeding frenzy which devoured material all around them. “We revealed, using state-of-the-art computer simulations, that the first generation of black holes – those born just a few hundred million years after the Big Bang - grew incredibly fast, into tens of thousands of times the size of our Sun.” The dense, gas-rich environments in early galaxies enabled short bursts of ‘super Eddington accretion’; a term used to describe what happens when a black hole “eats” matter faster than what is deemed normal. “These tiny black holes were previously thought to be too small to grow into the behemoth black holes observed at the centre of early galaxies,” Mr Mehta said. “What we have shown here is that these early black holes, while small, are capable of growing spectacularly fast, given the right conditions.” Black holes are broken down into two categories: ‘heavy seed’ and ‘light seed’. The light seed ones are relatively small to begin with – about 10 to several hundred times the mass of the Sun – growing to become what is termed super-massive once they reach millions of times the size of the Sun. Heavy ones, on the other hand, start off much bigger than their lighter counterparts, up to one hundred thousand times the mass of the Sun at birth. Until the research findings made by the research team at MU, astronomers thought that heavy seed types were required to explain the presence of the super-massive black holes found to reside at the centre of most large galaxies. However, Dr John Regan of MU’s Physics Department said: “Now we’re not so sure.” “Heavy seeds are somewhat more exotic and may need rare conditions to form. Our simulations show that your ‘garden variety’ stellar mass black holes can grow at extreme rates in the early Universe.” He continued: “The early Universe is much more chaotic and turbulent than we expected, with a much larger population of massive black holes than we anticipated too.” The results will have implications for the important joint European Space Agency-NASA Laser Interferometer Space Antenna (LISA) mission, scheduled to launch in 2035. "Future gravitational wave observations from that mission may be able to detect the mergers of these tiny, early, rapidly growing baby black holes,” Dr Regan added. Dr Lewis Prole, a postdoctoral fellow at MU and research team member, said that the discovery “unlocks one of astronomy’s big puzzles. “That being how black holes born in the early Universe, as observed by the James Webb Space Telescope, managed to reach such super-massive sizes so quickly.”