Recent observations from the James Webb Space Telescope (JWST) may provide clues to explain why the universe is expanding faster today compared to its early stages. Instead of measurement errors, the findings suggest a previously unknown mechanism within the universe may be at play.

The data serves as a vital cross-check for measurements from the Hubble Space Telescope, which have shown discrepancies in the universe’s expansion rate, known as the Hubble Tension. This conflict has puzzled cosmologists, as current models cannot fully account for it.

Nobel laureate Adam Riess, the lead author of the study, stated, “The inconsistency between the observed expansion rate and predictions from the standard model suggests gaps in our understanding of the universe. With confirmation from both NASA telescopes, we must take the Hubble Tension seriously. This is both a challenge and an exciting opportunity to learn more.”

Riess’s previous Nobel-winning research highlighted the accelerated expansion of the universe, attributed to a mysterious force called dark energy. This new study further investigates this phenomenon.

Measuring the Hubble Constant with JWST

Riess and his team used JWST’s extensive dataset from its first two years to verify Hubble’s measurements of the Hubble constant, the rate of the universe’s expansion. They focused on galaxies where Hubble had already conducted highly precise local measurements. The results from both telescopes closely aligned, ruling out significant biases in Hubble’s data and suggesting the tension is not due to measurement error.

However, the Hubble constant remains a mystery. While the standard model predicts a value of around 67-68 km/s/Mpc, actual telescope observations often range between 70 and 76 km/s/Mpc, with an average of 73 km/s/Mpc. This gap of 5-6 km/s/Mpc is too large to be attributed to statistical error alone.

Investigating the Hubble Tension

With JWST’s high-resolution data offering greater clarity, the study excluded measurement biases as the cause of the discrepancy. Researchers now suggest that unknown factors or gaps in the standard cosmological model may be responsible.

“Observing the universe with JWST is like seeing it in high definition for the first time, significantly enhancing our ability to analyze the data,” said Siyang Li, a graduate student at Johns Hopkins University and contributor to the study.

The research examined about one-third of Hubble’s galaxy sample, using the well-established distance of the galaxy NGC 4258 as a reference. Despite the smaller sample size, the measurements achieved remarkable accuracy, with deviations under 2%, far less than the 8-9% difference seen in the Hubble Tension.

Dark Energy and New Hypotheses on the Early Universe

While the Hubble constant has no direct impact on daily life, it is a crucial factor in understanding the universe’s large-scale evolution. Resolving the Hubble Tension could reveal deeper issues within the standard cosmological model, which already struggles to explain the nature of dark matter and dark energy, believed to constitute 96% of the universe.

Marc Kamionkowski, a cosmologist at Johns Hopkins University not involved in the study, suggested, “One possibility is that our understanding of the early universe is incomplete. There could be an unknown component, such as early dark energy, that accelerated the universe’s expansion after the Big Bang.”

Other theories include exotic particles, unusual dark matter properties, variations in electron mass, or even primordial magnetic fields. Kamionkowski added, “This is where theorists can get really creative.”

References:

• Artem Y. Burdanov et al. JWST Sighting of Decameter Main-Belt Asteroids and View on Meteorite Sources. Nature, 2024. DOI: 10.1038/s41586-024-08480-z.

Additional information available at: Science Daily and Hub at Johns Hopkins University.