Using helium, astronomers blow certainty into early Big Bang conditions

New observations regarding the composition of distant galaxies reveal insights into the earliest phases of the universe that confirm decades of scientific understanding of the elements and particles produced by the Big Bang, according to a new study.

Researchers used data from The Large Binocular Telescope (LBT) to measure the amount of helium — the second-most common element in the cosmos and a vital ingredient for the formation of life — in metal-poor nebulas, clouds of gas and dust in space where stars are sometimes born. Their findings strengthen long-held theories about how ancient elements, such as carbon and nitrogen, may have been dispersed in the period following the Big Bang.

Astronomers did this by analyzing helium signals in optical and infrared light to determine the temperature and density of the gases within faraway systems. After collecting 48 high-quality galactic samples, the team created a dataset aimed at significantly expanding researchers’ ability to infer the universe’s primordial helium abundance.

“Everything that we need to live here on Earth was once fused inside of a star,” said Miqaela Weller, lead author of the study and a PhD student in astronomy at The Ohio State University. “Understanding precisely where those elements come from helps inform us of how our universe evolved and how it will evolve in the future.”

The study was recently published as part of a series of papers in The Astrophysical Journal.

The work was completed as part of the LBT Yp project, a collaboration designed to accurately determine how much primordial helium was created at the universe’s beginning, an amount theorized to be largely dependent on the types of neutrinos, tiny and abundant subatomic particles, that were likely formed when the universe was only a second old.

If, for example, the amount of helium found in metal-poor galaxies is vastly different from astronomers’ current predictions, their results might challenge current theories about the universe’s early conditions as well as open the door to new, undiscovered physics, said Weller, who leads the infrared data reduction for the project

Still, it can be extremely difficult to peer into the universe’s past, as astronomers can only see up to about 400,000 years after the Big Bang, or when the universe became transparent enough to form the cosmic microwave background (CMB). Thus, by comparing their new observations with archival ones of the CMB, they can determine if current models of the universe are accurate.

“The importance of galactic archaeology cannot be understated,” said Weller. “The stars are within us, and learning more about them helps us determine our place within the universe.”

Roughly 90% of the universe’s helium formed during the Big Bang, with 10% originating from stars that have undergone nuclear fusion over the last 13.5 billion years. While researchers had previously only been able to estimate the universe’s helium abundance to a precision of about 2%, this work reduces that error to almost half a percent, a development that amounts to a huge leap in computational astrophysics, said Richard Pogge, a founding member of the project and a professor of astronomy at Ohio State.

“By making this exciting measurement, we’ve learned something fundamental about the universe,” said Pogge.

Scientists have theorized that all the raw materials of the universe emerged in the first few moments after its birth, including neutrinos. Until this paper’s result, it had been unclear whether the many subatomic particles that drive our modern grasp of particle physics appeared simultaneously or arrived later in an alternative, sequential way.

In searching for the answer, the team was challenged to locate extremely rare metal-poor galaxies, such as the tiny Leo P, as well as account for how Earth’s atmosphere could affect their data. Ultimately, their research confirmed that the number of neutrino species present at the Big Bang is, in fact, consistent with the standard model of particle physics, said Pogge.

“Finally having atomic data precise enough to show how the universe worked seconds after it began gives us the ability to make meaningful constraints on the nature of physics itself,” he said.

According to the team, the LBT Yp project plans to continue deciphering cosmic mysteries by constraining less-explored parameters of undiscovered metal-poor galaxies, likely with the aid of vast astronomical archives of collaboration projects like DESI.

“It’s going to take us many years to try to explore new galaxies and turn the techniques we’ve developed onto them,” Pogge said. “So it’s an enormous pleasure to be able to pass these decades-long findings onto those who are going to be the future of this field.”

Co-authors include Ohio State’s Jayde Spiegel as well as Evan Skillman and John H. Miller Jr. from the University of Minnesota, Erik Aver from Gonzaga University, Noah Rogers from Northwestern University, Danielle Berg from The University of Texas at Austin, and John Salzar from Indiana University. This work was supported by the National Science Foundation and Ohio State’s Center for Cosmology and AstroParticle Physics.