An illustration of a black hole's accretion disk emitting light. New research suggests that the black hole's elusive radiation, known as Hawking radiation, may have changed the structure of our universe. (Image credit: Gam-Ol via Pixabay)
Recent research suggests that a theoretical concept put forward by eminent physicist Stephen Hawking could influence the shape of the Universe.
In the 1970s, Hawking presented a revolutionary idea: black holes — commonly thought of as cosmic objects that swallow everything around them — could emit light similar to that emitted by hot objects. This effect, now called Hawking radiation, remains theoretical because of its extremely low intensity, calculated for stellar and supermassive black holes.
However, a new study published in the Journal of Cosmology and Astroparticle Physics suggests that this elusive radiation may have had a significant impact on the early structure of the universe. The scientists suggest that primordial black holes, likely to have existed shortly after the Big Bang, may have emitted powerful Hawking radiation, leaving a visible signature in the cosmos we see today.
“An intriguing possibility is that the early Universe may have gone through a phase in which its energy was dominated by primordial black holes, which then disappeared via Hawking radiation,” the researchers note in their paper. “This is a general consequence of ultra-light primordial black holes […], since even a small initial number of such objects would quickly become dominant in the expanding Universe.”
Decoding Hawking Radiation
In his seminal work, Hawking partially combined the mathematical underpinnings of general relativity and quantum mechanics — two key theories of physics that had not yet been fully unified — to explore the physics of black holes. He discovered that black holes, previously thought to be hopeless traps, can actually emit particles, including photons (light).
Importantly, the intensity of the radiation decreases as the mass of the black hole increases, meaning that black holes created by collapsing stars, as well as supermassive black holes holding galaxies, will emit so weakly that their Hawking radiation is undetectable by current instruments.
However, it is thought that much smaller black holes, each with a mass of less than 100 tons, may have formed in the early universe. These so-called primordial black holes may have emitted particles at high enough speeds to affect cosmic structures such as galaxies and clusters.
“Various cosmological scenarios predict the formation of black holes in the early Universe,” the authors write. “For example, primordial black holes could have arisen from the gravitational collapse of superdense regions.”
Remarkably, the Hawking radiation from these primordial black holes would include all sorts of particles, including hypothetical particles that weakly interact with the known particles described by the Standard Model. This implies that such radiation could provide a unique opportunity to study these elusive particles that are unlikely to be accessible in particle accelerators.
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