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Dark energy is created and contained in black holes

By examining data spanning nine billions of years, a team of scientists led by the University of Hawaiʻi at Mānoa has found the first observational evidence that black holes contain cores of dark energy, a mysterious force driving the accelerating expansion of the universe. Thus, instead of dark energy being spread out across spacetime, as many scientists have previously assumed, the new findings suggest that this energy was created and remains inside the (increasingly larger) black holes that formed in the crushing forces of collapsing stars.

The existence of dark energy was first proposed in the 1990s when investigations of distant stars revealed that the expansion of the universe was accelerating. This strange phenomenon – given that gravity should be slowing the universe’s expansion – made scientists ponder what could drive the expansion faster and led them to postulate dark energy as an unknown, mysterious force working against gravity. However, its precise nature and origins have not yet been clearly understood. Now, by connecting this force to the evolution of black holes over extended periods of time, the researchers have managed to shed new light on the nature of our universe. 

“We’re really saying two things at once: that there’s evidence the typical black hole solutions don’t work for you on a long, long timescale, and we have the first proposed astrophysical source for dark energy,’” said lead author Duncan Farrah, an astrophysicist at Hawai’i.

“What that means, though, is not that other people haven’t proposed sources for dark energy, but this is the first observational paper where we’re not adding anything new to the universe as a source for dark energy: black holes in Einstein’s theory of gravity are the dark energy.”

By comparing black hole masses in young galaxies, where stars are still forming, with black holes masses in old, so-called “dormant galaxies,” where no more stars are currently born, the scientists discovered that black holes in dormant galaxies are between seven to 20 times larger than expected, suggesting that black holes too are growing as the universe expands.

“Here’s a toy analogy. You can think of a coupled black hole like a rubber band, being stretched along with the universe as it expands,” explained co-author Kevin Croker, a cosmologist at Hawai’i. “As it stretches, its energy increases. Einstein’s E = mc2 tells you that mass and energy are proportional, so the black hole mass increases, too.”

“The importance of this work is that it’s taken the theories about black holes with dark energy cores and linked them for the first time to tangible observations of the universe,” concluded co-author Chris Pearson, an astronomer at the research institute RAL Space in Oxfordshire. “These black holes are expected to grow in mass as the universe expands.” 

The findings are synthetized in two articles published in The Astrophysical Journal and The Astrophysical Journal Letters.


By Andrei Ionescu, Staff Writer

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