Our universe appears to be expanding about eight percent faster than initially assumed possible, according to new observations from the James Webb Space Telescope.
There has been a long-established discrepancy between the observed expansion rate of the universe and the rate we thought possible based on our knowledge of the cosmos, which is known as the Hubble tension.
Now, according to a new paper in The Astrophysical Journal, new measurements from Webb have confirmed that the Hubble tension isn’t due to some flaw in our observations, but instead potentially due to the influence of dark matter and dark energy.
“The discrepancy between the observed expansion rate of the universe and the predictions of the standard model suggests that our understanding of the universe may be incomplete,” study co-author Adam Riess, a Nobel laureate and professor of physics and astronomy at Johns Hopkins University, said in a statement.
“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.”
NASA, ESA, and the Hubble Heritage Team STScI/AURA / ISTOCK / GETTY IMAGES PLUS
In the paper, the researchers describe how they analyzed data from the JWST’s first two years in space to calculate the rate at which galaxies were moving away from each other.
This new data confirms the findings of the Hubble Space Telescope that the universe is expanding faster today than it did during its first few billion years.
The rate of expansion of the universe today is a figure known as the Hubble constant, which is typically measured in units of kilometers per second per megaparsec (km/s/Mpc), where a megaparsec (Mpc) is about 3.26 million light-years.
Based on our knowledge of the universe, the Hubble constant should be lower than the value observed by the Hubble Space Telescope by around 5–6 km/s/Mpc. This difference, which cannot easily be explained by random errors or uncertainties, is the Hubble tension.
The JWST measurements were found to closely match those of the Hubble, meaning that the tension was not due to Hubble instrument error.
“The Webb data is like looking at the universe in high definition for the first time and really improves the signal-to-noise of the measurements,” co-author Siyang Li, a graduate student at Johns Hopkins University, said in the statement.
Therefore, the Hubble tension must be due to unknown gaps in our knowledge of the physics of the universe.
When Was the James Webb Telescope Launched?
The James Webb Space Telescope was launched on December 25, 2021, aboard an Ariane 5 rocket from the Guiana Space Centre in French Guiana.
A collaborative project between NASA, ESA (European Space Agency), and CSA (Canadian Space Agency), the JWST was sent to its operational location at the second Lagrange point (L2), approximately 1 million miles from Earth, and became fully operational for scientific observations in July 2022.
Observations in the late 1990s revealed that the rate of expansion of the universe has been accelerating since the Big Bang some 13.8 billion years ago, due to the influence of dark energy.
Dark energy is a mysterious and poorly understood form of energy that makes up approximately 68 percent of the universe’s total energy density. It appears to have a repulsive gravitational effect, counteracting the attractive force of gravity, leading to the acceleration of the universe’s expansion.
“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 Johns Hopkins cosmologist involved in calculating the Hubble constant who was not involved in this new study, said 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.”
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References
Riess, A. G., Scolnic, D., Anand, G. S., Breuval, L., Casertano, S., Macri, L. M., Li, S., Yuan, W., Huang, C. D., Jha, S., Murakami, Y. S., Beaton, R., Brout, D., Wu, T., Addison, G. E., Bennett, C., Anderson, R. I., Filippenko, A. V., & Carr, A. (2024). JWST Validates HST Distance Measurements: Selection of Supernova Subsample Explains Differences in JWST Estimates of Local H0. The Astrophysical Journal, 977(1), 120. https://doi.org/10.3847/1538-4357/ad8c21