A representation of the evolution of the universe over 13.77 billion years. NASA's Goddard Space Flight CenterAstronomers have long understood that the universe is expandingin other words, the space in between cosmic objects that arent bound by gravity is getting ever more vast. Then, in 1998, scientists discovered the universes 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 Hubbles measurementsand 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 universes expansion is accelerating in 1998.With two NASA flagship telescopes now confirming each others findings, we must take this [Hubble tension] problem very seriouslyits 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 universes 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. The Hubble Ultra Deep Field is a snapshot of about 10,000 galaxies in a tiny patch of sky, taken by NASAs Hubble Space Telescope. NASA, ESA, S. Beckwith (STScI), the HUDF TeamBut the curious thing was the rate they calculated. The universes 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 arent wrong, then perhaps its 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 elementsdark matter and dark energyand 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 universes 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 Sciences 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 matterearly dark energythat 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.Get the latest stories in your inbox every weekday.Filed Under: Astronomers, Astronomy, James Webb Space Telescope, Mysteries, New Research, Nobel Prizes, Outer Space, telescope, universe