Massive black hole mystery unlocked by Kildare University researchers

It’s one of astronomy’s great mysteries: how did black holes get so massive, so quickly. An answer to this cosmic conundrum has now been provided by Maynooth University (MU) researchers and reported today in Nature Astronomy.

“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,” says Daxal Mehta, a PhD candidate in the Department of Physics at the Kildare University, who led the research.

“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 full research paper is available HERE.

“This breakthrough unlocks one of astronomy’s big puzzles,” says Dr Lewis Prole, a postdoctoral fellow at MU and research team member. “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.”

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’s normal or safe. So fast, that it should blow its food away with light but somehow keeps eating it anyway.

The results provided a ‘missing link’ between the first stars and the super massive black holes that came much later.

“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,” says Daxal Mehta.

“What we have shown here is that these early black holes, while small, are capable of growing spectacularly fast, given the right conditions,” he adds.

Black holes come in ‘heavy seed and ‘light seed’ types.

The light seed types are relatively small to begin with, only about ten to a few hundred times the mass of our Sun at most and must grow from there to become ‘supermassive’ – millions of times the mass of the Sun.

The heavy types on the other hand start life already much more massive, perhaps up to one hundred thousand times the mass of the Sun at birth.

Up to now, 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.

“Now we’re not so sure,” says Dr John Regan of MU’s Physics Department and research group leader.

“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.”

The MU research reshapes the understanding of black hole origins but also highlights the importance of high-resolution simulations in uncovering the Universe’s earliest secrets.

“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,” says Dr Regan.

The results also 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,” says Dr Regan. 

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