A Simon Fraser University cosmologist believes his team's new research may bring them a step closer to cracking one of science's biggest questions - the Hubble tension.
The quest to determine how fast the universe is expanding has irked cosmologists for decades, leading it to be dubbed the Hubble tension - or even the Hubble crisis.
But new findings, published in Nature Astronomy, could help to finally answer the cosmic question.
"This is an exciting moment for us and the wider cosmology community because our idea could address two major unsolved puzzles about our universe - the Hubble tension and the origin of cosmic magnetic fields," says Levon Pogosian, professor and department chair at SFU Physics, and co-author of the paper.
"Solving these puzzles would be like opening a new window into the early universe. It would help cosmologists to better explain the origin of the universe and everything within it."
The researchers' theory centres on primordial magnetic fields, tiny magnetic fields that may have existed from the dawn of time.
They argue that primordial magnetic fields could have accelerated the process of recombination - when electrons and protons combined to form atoms - changing the patterns in the cosmic microwave background.
In turn, this would affect how scientists extract from the data the value of the Hubble constant, the unit describing how fast the universe is expanding today.
Releasing the tension
The Hubble tension is named after pioneering astronomer Edwin Hubble, who observed that distant galaxies are all moving away from ours.
However, the actual speed at which the universe is expanding has perplexed cosmologists, as two precise ways of measuring its expansion rate come up with very different answers.
This discrepancy, referred to as the Hubble tension, is considered one of the hottest topics in cosmology.
"It's a major headache for cosmologists across the world. It has sprung an industry of scientists inventing new ingredients in the cosmological model to try to address the Hubble tension," says Pogosian.
"But what we're saying is that the ingredient, the magnetic fields, could have been there all this time. And, if confirmed, it would also explain the origin of magnetic fields observed throughout the cosmos."
Over the last three years, Pogosian's collaborators, Karsten Jedamzik from University of Montpelier, Tom Abel from Stanford University, and Yacine Ali-Haimoud from New York University, have been using SFU's supercomputer to simulate the process of recombination in great detail.
The results were then used to crunch data from the Hubble telescope, the Planck satellite and other telescopes, to test their theory.
"Remarkably, our findings show that the idea survives the most detailed and realistic tests available today," says Pogosian.
"More importantly, they provide clear targets for future observations. Over the next several years, we will learn whether tiny magnetic fields from the dawn of time really helped shape the universe we see today, and whether they hold the key to resolving the Hubble tension once and for all."
SFU's Cedar supercomputer, and its successor Fir, played a fundamental role in the team's research.
"We wouldn't have been able to carry out our research without the supercomputer. It was crucial for our tests and calculations," says Pogosian.
"The supercomputer allowed us to break down our tests into smaller jobs and run them in parallel, which saved us a huge amount of time."
A Cosmic Clue Hidden in Magnetism: How Primordial Magnetic Fields May Help Resolve the Hubble Tension - find out more here
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LEVON POGOSIAN, professor and department chair at SFU Physics
