Dark Energy Mystery: Mounting Evidence Points to Black Holes As Hidden Source

By University of Michigan November 1, 2024

Collected at: https://scitechdaily.com/dark-energy-mystery-mounting-evidence-points-to-black-holes-as-hidden-source/

The Dark Energy Spectroscopic Instrument (DESI) is helping researchers explore the ‘Big Bang played in reverse’.

Scientists using data from DESI are exploring a groundbreaking theory that connects black holes to the universe’s accelerating expansion. The theory suggests that dark energy, which constitutes about 70% of the universe and drives its expansion, may originate from processes occurring within black holes, akin to a reverse Big Bang.

Exploring the Dark Energy Enigma

Nearly 14 billion years ago, at the onset of the Big Bang, a mysterious energy triggered an exponential expansion that created all known matter. This event, described by the inflationary universe theory, set the stage for the cosmos as we know it.

This ancient energy shares some key properties with the dark energy present in today’s universe—a profound mystery. Dark energy makes up about 70% of the universe, yet its nature remains elusive to scientists.

JWST Imaging of Star Forming Protocluster — JWST NIRCam imaging of star-forming protocluster PHz G191.24+62.04, 11 billion years ago as the universe was approaching the peak of star formation. These early galaxies are among the most active star-forming galaxies observed between 10.5 and 11.5 billion years ago. Each galaxy seen in this image is therefore producing many black holes, which are converting matter into dark energy according to the cosmologically coupled black hole hypothesis. This image shows the two “modules” of JWST NIRCam: The leftmost module contains the protocluster, and the rightmost module is an adjacent blank field. Each module sees thousands of galaxies. Credit: NASA, ESA, CSA, Maria Polletta (INAF), Hervé Dole (Paris), Brenda Frye (UofA), Jordan C. J. D’Silva (UWA), Anton M. Koekemoer (STScI), Jake Summers (ASU), Rogier Windhorst (ASU)

The Reverse Big Bang Theory

“If you ask yourself the question, ‘Where in the later universe do we see gravity as strong as it was at the beginning of the universe?’ the answer is at the center of black holes,” said Gregory Tarlé, a physics professor at the University of Michigan and co-author of the study. “It’s possible that what happened during inflation runs in reverse, the matter of a massive star becomes dark energy again during gravitational collapse—like a little Big Bang played in reverse.”

In a recent study published in the Journal of Cosmology and Astroparticle Physics, Tarlé and collaborators from five institutions present new evidence supporting this idea, gathered using data from the Dark Energy Spectroscopic Instrument (DESI). DESI, comprising 5,000 robotic eyes on the Mayall Telescope at Kitt Peak National Observatory on the Tohono O’odham Nation’s land, offers fresh insights into the relationship between black holes and dark energy

Black Holes and Cosmic Acceleration

“If black holes contain dark energy, they can couple to and grow with the expanding universe, causing its growth to accelerate,” said Kevin Croker, lead author of the team’s new study and an assistant research scientist at Arizona State University. “We can’t get the details of how this is happening, but we can see evidence that it is happening.”

Data from the first year of DESI’s planned five-year survey shows tantalizing evidence 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.

“When I first got involved with the project, I was very skeptical,” said co-author Steve Ahlen, professor emeritus of physics at Boston University. “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.’”

DESI Telescope — DESI was mounted on the 4-meter Mayall Telescope at Kitt Peak National Observatory. Kitt Peak National Observatory (KNPO) is located 56 miles southwest of Tucson, Arizona, in the Schuk Toak District on the Tohono O’odham Nation. KPNO is administered by the NSF’s National Optical-Infrared Astronomy Research Laboratory (NSF’s OIR Lab) in Tucson. The Mayall Telescope is a reflector telescope with a 4-meter primary mirror that sits on an equatorial mount. It is the largest of the 22 optical telescopes located on Kitt Peak. It was commissioned in 1973 and it is nearly identical to the 4-meter Blanco Telescope at the Cerro Tololo Inter-American Observatory in Chile, also operated by NSF’s OIR Lab and commissioned in 1976. Credit: DESI Collaboration

Analyzing Galactic Data

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 be used to determine how fast the universe is expanding with exquisite precision. In turn, these data can be used 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.

“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,” said Duncan Farrah, associate professor of physics at the University of Hawai’i and co-author of the study. “This makes it more plausible that black holes are the source of dark energy.”

Further Investigations Into 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.

“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,” said Brian Cartwright, an astrophysicist, co-author, and former general counsel of the U.S. Securities and Exchange Commission.

The Evolving Study 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.

“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,” said co-author Rogier Windhorst, an interdisciplinary scientist for the JWST and professor of earth and space exploration at Arizona State University.

“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,” Croker said.

Future Prospects in Dark Energy Research

Science demands more avenues of inquiry and observations, and now that DESI is online, this exploration for dark energy is just getting started.

“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,” Ahlen said. “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.

“Fundamentally, whether black holes are dark energy, coupled to the universe they inhabit, has ceased to be just a theoretical question,” Tarlé said. “This is an experimental question now.”

Reference: “DESI dark energy time evolution is recovered by cosmologically coupled black holes” by Kevin S. Croker, Gregory Tarlé, Steve P. Ahlen, Brian G. Cartwright, Duncan Farrah, Nicolas Fernandez and Rogier A. Windhorst, 28 October 2024, Journal of Cosmology and Astroparticle Physics.
DOI: 10.1088/1475-7516/2024/10/094