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Universe’s expansion: Fast radio bursts help solve mystery

Science desk || shiningbd

Published: 12:39, 22 April 2021  
Universe’s expansion: Fast radio bursts help solve mystery

Short-lived bursts of radio waves from deep space, possibly from eruptions on magnetic stars (one illustrated), are now being used to measure the expansion of the universe

Astronomers have been arguing about the rate of the universe’s expansion for nearly a century. A new independent method to measure that rate could help cast the deciding vote.

For the first time, astronomers calculated the Hubble constant — the rate at which the universe is expanding — from observations of cosmic flashes called fast radio bursts, or FRBs.

While the results are preliminary and the uncertainties are large, the technique could mature into a powerful tool for nailing down the elusive Hubble constant, researchers report April 12 at arXiv.org.

Ultimately, if the uncertainties in the new method can be reduced, it could help settle the longstanding debate that holds our understanding of the universe’s physics in the balance (SN: 7/30/19).

“I see great promises in this measurement in the future, especially with the growing number of detected repeated FRBs,” says Stanford University astronomer Simon Birrer, who was not involved with the new work.

Astronomers typically measure the Hubble constant in two ways. One uses the cosmic microwave background, the light released shortly after the Big Bang, in the distant universe. The other uses supernovas and other stars in the nearby universe.

These approaches currently disagree by a few percent. The new value from FRBs comes in at an expansion rate of about 62.3 kilometers per second for every megaparsec (about 3.3 million light-years). While lower than the other methods, it’s tentatively closer to the value from the cosmic microwave background, or CMB.

“Our data agrees a little bit more with the CMB side of things compared to the supernova side, but the error bar is really big, so you can’t really say anything,” says Steffen Hagstotz, an astronomer at Stockholm University. Nonetheless, he says, “I think fast radio bursts have the potential to be as accurate as the other methods.”

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