- Dark energy is a mysterious force that drives the accelerating expansion of our universe. Scientists believe dark energy makes up about 70% of the universe, but we don’t yet know what it is.
- Scientists suggest black holes may be the source of dark energy. They said that when matter from a huge star collapses into a black hole, it could produce dark energy.
- Using data from the Dark Energy Spectroscopic Instrument (DESI), scientists found the density of dark energy increased in time along with how the amount and mass of black holes increased in time.
The University of Michigan published this original story on October 30, 2024. Edits by EarthSky.
Evidence for black holes as the source of dark energy
Dark energy is one of the biggest mysteries in the universe. Scientists believe dark energy makes up about 70% of the universe, but we don’t yet know what it is. A team of scientists said on October 30, 2024, that they used data from the Dark Energy Spectroscopic Instrument (DESI) to show that the density of dark energy increased in time. This provides a compelling clue supporting this idea of what dark energy is, the researchers said, because that increase in time agrees with how the amount and mass of black holes increased in time.
Kevin Croker is the lead author from Arizona State University. Croker said:
If black holes contain dark energy, they can ‘couple’ to and grow with the expanding universe, causing its growth to accelerate. We can’t get the details of how this is happening, but we can see evidence that it is happening.
On October 28, 2024, the Journal of Cosmology and Astroparticle Physics published the team’s peer-reviewed study. In it, the team from five institutions strengthen the case for black holes producing dark energy with recent data from DESI, which consists of 5,000 robotic eyes mounted on the Mayall Telescope at Kitt Peak National Observatory on the land of the Tohono O’odham Nation in Arizona.
Co-author Steve Ahlen of Boston University said:
When I first got involved with the project, I was very skeptical. But I maintained an open mind throughout the entire process and when we started doing the cosmology calculations, I said, ‘Well, this is a really nice mechanism for making dark energy.’
Looking at distant galaxies
To search for evidence of dark energy from black holes, the team used tens of millions of distant galaxies measured by DESI. The instrument peers billions of years into the past and collects data that can help determine how fast the universe is expanding with exquisite precision. In turn, scientists can use these data to infer how the amount of dark energy is changing in time.
The team compared these data to how many black holes were being made in the deaths of large stars across the history of the universe.
Co-author Duncan Farrah of the University of Hawai’i said:
The two phenomena were consistent with each other … as new black holes were made in the deaths of massive stars, the amount of dark energy in the universe increased in the right way. This makes it more plausible that black holes are the source of dark energy.
Mounting evidence for black holes as the source of dark energy
This research complements a growing body of literature studying the possibility of cosmological coupling in black holes. A 2023 study, involving many of the authors on this paper, reported cosmological coupling in supermassive black holes within galactic centers. That 2023 report encouraged other teams to search for the effect in black holes across all the different places they can be found in the universe.
Co-author Brian Cartwright, former general counsel of the U.S. Securities and Exchange Commission, said:
Those papers investigate the link between dark energy to black holes by their rate of growth. Our new paper links black holes to dark energy by when they are born.
A survey of black holes
A key difference in the new paper is that the majority of the relevant black holes are younger than those previously examined. These black holes were born in an epoch when star formation – which tracks black hole formation – was well underway, rather than just beginning.
Co-author Rogier Windhorst of Arizona State University said:
This occurs much later in the universe and is informed by recent measurements of black hole production and growth as observed with the Hubble and Webb space telescopes.
Croker said:
The next question is where these black holes are, and how they have been moving around for the past 8 billion years. Scientists are working to constrain this right now.
From theory to experiment
Science demands more avenues of inquiry and observations, and now that DESI is online, this exploration for dark energy is just getting started. Ahlen said:
This will only bring more depth and clarity to our understanding of dark energy, whether that continues to support the black hole hypothesis or not. I think as an experimental endeavor, it’s wonderful. You can have preconceived notions or not, but we’re driven by data and observations.
Regardless of what those future observations bring, the work happening now represents a sea change in dark energy research, the team said. Co-author Gregory Tarlé of the University of Michigan said:
Fundamentally, whether black holes are dark energy, coupled to the universe they inhabit, has ceased to be just a theoretical question. This is an experimental question now.
Bottom line: Astronomers have found more evidence that black holes are the source of mysterious dark energy, which makes up 70% of our universe.
Source: DESI dark energy time evolution is recovered by cosmologically coupled black holes
Via University of Michigan
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