James Webb Telescope Confirms the Universe Is Expanding Faster Than We Thought—and Scientists Still Don’t Know Why

Astronomers have long understood that the universe is expanding—in other words, the space in between cosmic objects that aren’t bound by gravity is getting ever more vast. Then, in 1998, scientists discovered the universe’s rate of expansion is accelerating.

In the years since, researchers using the Hubble Space Telescope have observed that the current expansion rate, called the Hubble constant, is faster than what standard cosmology models estimate it should be. This mystery of inconsistent measurements has been dubbed the Hubble tension.

Now, a team of researchers has used data from the James Webb Space Telescope (JWST) to confirm Hubble’s measurements—and thus, the mystery persists. Their study, published Monday in The Astrophysics Journal, suggests the discrepancy may be caused by an as-yet unknown feature in the universe, rather than an error in telescope measurement.

The finding “suggests that our understanding of the universe may be incomplete,” Adam Riess, an astrophysicist at Johns Hopkins University and lead author of the study, says in a statement. Riess co-received the 2011 Nobel Prize in Physics for discovering that the universe’s expansion is accelerating in 1998.

“With two NASA flagship telescopes now confirming each other’s findings, we must take this [Hubble tension] problem very seriously—it’s a challenge but also an incredible opportunity to learn more about our universe,” he adds in the statement.

Riess and his team used JWST data to measure the distances from Earth to specific kinds of galaxies with pulsating stars called Cepheid variables, which are “the gold standard for measuring cosmic distances,” per the statement. With these measurements, they calculated the universe’s rate of expansion. The JWST results were consistent with the Hubble ones, which effectively rules out the possibility of the Hubble tension resulting from human or instrument error.

But the curious thing was the rate they calculated. The universe’s expansion rate is expressed in kilometers per second per megaparsec. (A megaparsec equals 3.26 million light-years.) Widely accepted cosmology models have used light from the early universe to put the Hubble constant of universe expansion at about 67 to 68 km/s/Mpc.

The now-confirmed telescope observations, however, yield an average of 73 km/s/Mpc.

As Emilee Speck puts it for FOX Weather, “the problem with science is that answering one question creates many more.” If the measurements aren’t wrong, then perhaps it’s the standard cosmology models that are flawed.

“Yes, it appears there is something missing in our understanding of the universe,” Riess tells Reuters’ Will Dunham. “Our understanding of the universe contains a lot of ignorance about two elements—dark matter and dark energy—and these make up 96 percent of the universe, so this is no small matter.”

Dark matter, hypothesized to make up 27 percent of the universe, is some unknown material that affects the rest of the cosmos with its gravity. Dark energy, on the other hand, is thought to make up some 68 percent of the universe, and scientists speculate it might be responsible for the universe’s expansion. And now, the new findings suggest it perhaps accounts for the unexplained acceleration of that expansion, too.

“The more work we do, the more it is apparent that the cause is something much more interesting than a telescope flaw,” Riess tells Live Science’s Ben Turner. “[The] next steps are many. More data on many fronts and new ideas are needed.”

“One possible explanation for the Hubble tension would be if there was something missing in our understanding of the early universe, such as a new component of matter—early dark energy—that gave the universe an unexpected kick after the Big Bang,” Marc Kamionkowski, a cosmologist at Johns Hopkins who helped calculate the Hubble constant but was not involved in the new study, says in the statement. “And there are other ideas, like funny dark matter properties, exotic particles, changing electron mass or primordial magnetic fields that may do the trick. Theorists have license to get pretty creative.”

Margherita Bassi | READ MORE

Margherita Bassi is a freelance journalist and trilingual storyteller. Her work has appeared in publications including BBC Travel, Discover magazine, Live Science, Atlas Obscura and Hidden Compass.