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If “ insanely large ” black holes, those with a mass over 100 billion times that of the Sun, exist in the Universe, they would provide a powerful tool for cosmological testing due to their unique fingerprints, according to one article published in the Monthly notices from the Royal Astronomical Society.
Carr et al. studied how incredibly large black holes could form and the potential limits of their size. Image Credit: NASA’s Goddard Space Flight Center.
“Black holes are a key prediction of general relativity,” Queen Professor Emeritus Mary Bernard Carr and colleagues said.
“There is a plethora of observations indicating their existence in the solar or intermediate mass range. In particular, the existence of binary black holes in the mass range between 10 and 50 solar masses has been demonstrated by the detection of gravitational waves from inspiring binaries.
“There is also evidence of supermassive black holes at the center of galaxies, including Sagittarius A * at the center of our own Milky Way galaxy, with a mass of 4 million solar masses.
“Recently, shadow imagery created by M87 *, the supermassive black hole at the center of the giant elliptical galaxy M87 with a mass of 6.5 billion solar masses, was reported by the Event Horizon telescope.
“Supermassive black holes in galactic nuclei cover a wide mass range, extending up to nearly 100 billion solar masses,” they said.
“The current heaviest black hole is associated with the TON 618 quasar and has a mass of 70 billion solar masses, while the second heaviest, at the center of the galaxy IC 1101, has a mass inferred from its radio emission of 40 billion solar masses. “
“This raises the question of whether there might be even larger black holes in galactic nuclei and whether there is indeed a natural upper limit to the mass of a supermassive black hole.”
In their new paper, Professor Carr, Dr Florian Kühnel from the Ludwig-Maximilians-Universitat and Dr Luca Visinelli from the University of Amsterdam suggest that incredibly large black holes (SLABs) could be primordial, forming early of the Universe, and well before the galaxies.
Since primordial black holes do not form from a collapsing star, they could have a wide range of masses, including very small and incredibly large.
“Although there is currently no evidence for the existence of SLABs, it is conceivable that they could exist and that they could also reside outside galaxies in intergalactic space, with consequences of d ‘interesting observation,’ said Professor Carr.
“However, surprisingly, the idea of SLABs has been largely overlooked until now.”
“We have offered options on how these black holes might form and hope our work begins to motivate discussions within the community.”
If SLABs are of primordial origin, this raises an interesting connection with the suggestion that primordial black holes could provide dark matter.
While the SLABs themselves clearly cannot do this, because they are too large to reside in galactic halos, it is possible that primordial black holes provide dark matter in a much lower mass range.
“The SLABs themselves couldn’t provide dark matter,” said Professor Carr.
“But if they do exist, it would have important implications for the Early Universe and make it plausible that lighter primordial black holes could do so.”
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Bernard carr et al. 2021. Stresses on insanely large black holes. MNRAS 501 (2): 2029-2043; doi: 10.1093 / mnras / staa3651
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