At a Glance
- Scientists have long debated the Hubble constant due to differing measurements from the early and present universe, raising questions about the accuracy of the Standard Model.
- A new study using data from the James Webb and Hubble space telescopes has reconciled these differences, showing the Hubble constant to be 70.4 km/s/Mpc with only a 3 percent error.
- The researchers improved precision by measuring supernovae and nearby galaxies, a challenging method that provides greater insight than examining the distant universe.
- The JWST’s advanced resolution and ability to see through cosmic dust allowed for significantly more accurate distance measurements, helping resolve past inconsistencies.
- These findings support the current Standard Model and suggest that the Hubble constant is likely not the key to solving mysteries like dark energy or dark matter.
Scientists have been trying to figure out how fast the universe is expanding, a question known as the Hubble constant. This constant helps us understand the age of the universe and its future. However, there has been some confusion because measurements of the Hubble constant have been different depending on whether scientists looked at the early universe or measured it in the present day. New data from the James Webb Space Telescope (JWST) and the Hubble Space Telescope may have solved this mystery. A study by Professor Wendy Freedman from the University of Chicago found that, after refining their measurements, the Hubble constant no longer appears to conflict with the Standard Model of the universe.
The study combined data from the JWST and the Hubble Space Telescope to get more accurate measurements of the Hubble constant. Freedman’s team focused on measuring distances in galaxies near our own, an approach that is much more difficult than looking back in time. To do this, scientists use the light from supernovae, which are exploding stars, to calculate the distance of galaxies. The new findings from the study show that the Hubble constant is 70.4 kilometers per second per megaparsec, with a margin of error of only about 3%. This is very close to previous measurements from the early universe, which had shown a rate of 67.4 kilometers per second per megaparsec.
The breakthrough came because of the JWST’s high precision, which has much better resolution and sensitivity than earlier telescopes. This allowed the team to measure the brightness of stars in galaxies with incredible accuracy and even see through cosmic dust that previously interfered with measurements. This is crucial because cosmic dust can block light from distant stars, making it harder to measure distances accurately. The JWST’s ability to “see” through this dust helped refine the data significantly.
This new research, whose results were published in The Astrophysical Journal, helps to confirm that the Standard Model, which has long been used to describe the universe, is still accurate. Scientists had previously wondered if the differences in measurements were pointing to new physics. However, this new data shows that the Hubble constant might not be the place to look for answers about dark matter or dark energy, two unsolved mysteries. Freedman and her team plan to use the JWST to measure the Hubble constant in more galaxies to continue refining these measurements and answer even more questions about the universe’s expansion.
References
- Freedman, W. L., Madore, B. F., Hoyt, T. J., Jang, I. S., Lee, A. J., & Owens, K. A. (2025). Status report on the chicago-carnegie hubble program (Cchp): Measurement of the hubble constant using the hubble and james webb space telescopes. The Astrophysical Journal, 985(2), 203. https://doi.org/10.3847/1538-4357/adce78
- Lerner, L. & University of Chicago. (2025, May 27). Webb telescope helps refine Hubble constant, suggesting resolution to long-standing expansion rate debate. Phys.Org; University of Chicago. https://phys.org/news/2025-05-webb-telescope-refines-hubble-constant.html
