New Study Reveals No Evidence of Discrepancy in the Hubble Constant

In collaboration with the Chicago-Carnegie Hubble program, astronomers utilizing the NASA/ESA/CSA James Webb Space Telescope have conducted new measurements of the Hubble constant. The findings align with the prevailing Lambda Cold Dark Matter (λCDM) model without necessitating the introduction of additional new physics.

“Emerging evidence indicates that standard models of the cosmos remain robust,” stated Professor Wendy Friedman from the University of Chicago.

“While this doesn’t rule out potential inconsistencies with the model in the future, it currently appears consistent concerning the Hubble constant.”

Presently, there are two primary methods for calculating the rate of the universe’s expansion.

The first method involves measuring the residual light from the Big Bang, which still permeates the universe.

This radiation, referred to as the cosmic microwave background, provides astronomers with insights into the universe’s early conditions.

Professor Friedman and her colleagues focus on the second method, which assesses the current rate of expansion in our local astronomical context.

Ironically, this approach poses more challenges than retracing cosmic history due to the difficulty of accurately measuring distances.

Over the last fifty years, scientists have developed several techniques to measure relatively nearby distances.

One method relies on detecting the light from a specific category of stars at their brightest moment when they explode as supernovae at the end of their lifecycle.

By knowing the peak brightness of these supernovae, astronomers can gauge their apparent luminosity and determine the distance.

Further observations reveal how fast the galaxy that the supernova originated from is moving away from us.

Images of CMB radiation captured by the Atacama cosmological telescope, where orange and blue signify differing radiation strengths. Image credit: ACT collaboration.

Professor Friedman has advanced two additional techniques utilizing knowledge from other star types: giant red stars and carbon stars.

However, considerable adjustments are necessary before finalizing these distance measurements.

Astronomers first need to account for cosmic dust that dims the light coming from these distant stars within our galaxy.

It is also critical to verify and correct for any luminosity variations that may occur over time and space.

Lastly, correction for any subtle measurement errors from the instruments utilized is essential.

Fortunately, technological advancements, such as the launch of the more powerful Webb telescope in 2021, have enabled scientists to refine these measurements significantly.

“We have more than doubled the sample of galaxies used to calibrate supernovae,” Professor Friedman noted.

“Statistical enhancements are valuable and will greatly improve the findings.”

The latest calculations from the team, which incorporate data from both the Hubble and Webb telescopes, yield a value of 70.4 km per second, with a margin of error of 3% per megaparsec.

This brings the value into statistical alignment with recent measurements from cosmic microwave background observations at 67.4 km per megaparsec, with an accuracy of plus or minus 0.7%.

The Webb telescope, with four times the resolution of Hubble, allows for the identification of individual stars that were previously recorded as blurry groupings.

It also offers enhanced precision and is approximately ten times more sensitive, enabling the detection of significant objects.

“We’re truly witnessing how remarkable the Webb telescope is for accurately measuring distances to galaxies,” stated Dr. Taylor Hoyt, a researcher at Lawrence Berkeley Laboratory.

“Its infrared detectors can penetrate the dust that has historically impeded precise distance measurements, enabling much more accurate brightness assessments of stars.”

“Astrophysicists are striving to formulate a theory that might elucidate varying rates of expansion as the universe ages,” Professor Friedman remarked.

“There are over a thousand scholarly papers addressing this issue, and it proves to be exceptionally challenging.”

The team’s research paper was published on May 27th in the Astrophysical Journal.

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Wendy L. Friedman et al. 2025. Status Report on the Chicago Carnegie Hubble Program (CCHP): Measurement of Hubble constants using Hubble and James Webb’s Space Telescopes. APJ 985, 203; doi:10.3847/1538-4357/adce78