Noble-Prize laureate Subrahmanyan Chandrasekhar, for whom NASA’s Chandra X-Ray Observatory was named, described black holes as “the most perfect macroscopic objects there are in the universe: the only elements in their construction are our concepts of space and time,” which has inspired astrophysicists to question how big these paradoxical objects, these “Gates of Hell” might become?
A team of scientists now suggest that these behemoths lurking at the centers of galaxies could reach “stupendously large” sizes–where the higher their mass, the greater their power–“they would be like a mini, galaxy-sized Big Bang,” according to Julie Hlavacek-Larrondo, at Université de Montréal, who holds the Canada Research Chair in Observational Astrophysics of Black Holes. These enigmatic objects, as affirmed by quantum theory, could be incredibly complex and concentrate an enormous amount of information inside themselves –the largest hard disk that exists in nature, in two dimensions.
“Stupendously Large Black Holes” (SLABs)
Discovering such gargantuan black holes may shed light on the nature of a significant fraction of the mysterious dark matter. These “stupendously large black holes” (SLABs) in galactic nuclei, exist in theory and may have been seeded by primordial black holes, suggests Florian Kuhnel who holds the Chair on Cosmology at the Arnold Sommerfeld Center for Theoretical Physics. The largest known black hole in the observable universe is powering the quasar TON 618 with a mass of 66 billion solar masses, leading to conjectures that even larger exist either within or beyond the observable universe, and to question if there is any upper limit to their sizes.
Primordial Black Holes –Source of Dark Matter?
Which leads to the speculation that primordial black holes formed during the cosmic Dark Age following the Big Bang, before the formation of the first stars.” It’s been hypothesized that there could be black holes that formed in the very early universe before stars existed at all,” said Savvas Koushiappas, a dark-matter physicist at Brown University, about the possibility that with future gravitational wave experiments, we’ll be able to look back to a time before the formation of the first stars to see if black hole events existed before stars formed in the cosmos, then we’ll know that those black holes are not of stellar origin.
Gravity Wells at Big Bang
These primordial black holes, gravity wells formed just moments after the Big Bang could be an explanation for dark matter. Shortly after the Big Bang, quantum mechanical fluctuations led to the density distribution of matter that we observe today in the expanding universe. Some of those density fluctuations might have been large enough to result in black holes peppered throughout the universe, suggested Koushiappas, coauthor of the 2017 study with Harvard’s Avi Loeb. The study outlined how scientists could use gravitational wave experiments to test the existence of primordial black holes first proposed in the early 1970s by Stephen Hawking and collaborators but have yet to be detected.
“Either primordial black holes exist, or the early universe evolved in a way that’s very different from the standard cosmological model. Either would be very important discoveries, say Koushiappas and Loeb. Primordial black holes, suggest Loeb and Koushiappas, fall into a category of entities known as MACHOs, or Massive Compact Halo Objects. Some scientists have proposed that dark matter—the unseen stuff that is thought to comprise most of the mass of the universe—may be made of MACHOs in the form of primordial black holes. A detection of primordial black holes would bolster that idea, while continued non-detection would cast doubt upon it.
“The really exciting thing about primordial black holes is that there are so many mysteries that in principle they could explain,” says Stephen Hawking’s colleague, physicist Bernard Carr. “Not the least of them being the existence of dark matter and dark energy.”
“One exciting possibility is that a population of primordial black holes may have created dark matter in the early universe,” wrote Dan Hooper, head of the theoretical astrophysics group at Fermilab in reply to to an email from Daily Galaxy, asking Hooper what new physics could be revealed by the discovery of these elusive relics. “If these black holes were initially lighter than a million kilograms or so,” Hooper added, “they would have evaporated in the first second after the Big Bang. In the process of this evaporation, they could have created any number of exotic forms of matter and energy, including dark matter.”
The Daily Galaxy, Max Goldberg, via Arxiv.org, New Scientist, Bernard Carr, Primordial Black Holes as Dark Matter, Did Black Holes Exist Before Stars and Primordial Black Holes as Dark Matter
Image credit: Shuttertstock License
Editor’s Note: The opening quote about the nature of black holes was incorrectly attributed to Albert Einstein.