Their measurement, 70 kilometers per second per megaparsec, overlaps the other major method for the Hubble constant.
Hubble tension?
This number, known as the Hubble constant, is essential for understanding the backstory of the universe.
“Confirming the reality of the Hubble constant tension would have significant consequences for both fundamental physics and modern cosmology,” explained Freedman.
This apparent mismatch has become known as the “Hubble tension.”
Although there is still much to learn about our universe, astronomers cannot agree on how quickly it is expanding. It’s worth noting that during the last twenty years, there have been two main methods for calculating this number, sometimes referred to as the “Hubble constant,” and the results have varied. This has led some people to question whether our understanding of the universe’s functioning is incomplete.
However, fresh data from the potent James Webb Space Telescope appears to indicate that the conflict, sometimes referred to as the “Hubble tension,” might not even exist.
Cosmologer Wendy Freedman of the University of Chicago and her colleagues analyzed new data acquired by NASA’s powerful James Webb Space Telescope and published their findings in a paper that was accepted to The Astrophysical Journal and is currently accessible on the arXiv preprint server. They determined the separation between ten nearby galaxies and determined a new value for the current expansion rate of the universe.
They overlap the other major method for the Hubble constant with their measurement of 70 km/s per megaparsec.
“We do not find strong evidence for a Hubble tension based on these new JWST data and using three independent methods,” stated astronomer and University of Chicago professor of astronomy and astrophysics Freedman. In contrast, it appears that the standard cosmological model that we used to explain the universe’s evolution is still relevant. “.
What is Hubble tension?
Since 1929, when University of Chicago alum Edwin Hubble (SB 1910, Ph. C. 1917) measured star distances, revealing that galaxies farther away from Earth were vanishing more quickly than those closer to home. However, determining the precise rate of the universe’s current expansion has proven to be surprisingly challenging.
To comprehend the history of the universe, one must know this value, also referred to as the Hubble constant. It is a crucial component of our model of the universe’s evolution through time.
“Both fundamental physics and modern cosmology would be significantly affected if the Hubble constant tension were proven to exist,” Freedman stated.
Scientists test these measures using a variety of techniques to ensure maximum accuracy because of their significance and difficulty.
Studying the cosmic microwave background, or leftover light from the Big Bang, is one important method. The most accurate estimate of the Hubble constant that can currently be obtained using this method is 67.4 km/s per megaparsec.
Using stars whose brightnesses are known, Freedman specializes in the second major method: measuring the expansion of galaxies in our local cosmic neighborhood directly. The stars appear progressively fainter at larger and greater distances, much like automobile lights do when they are far away. The rate of expansion of the universe can then be determined by measuring the distances between galaxies and their speed of motion away from us.
A higher value for the Hubble constant—closer to 74 km/s per megaparsec—was obtained in the past using this technique for measurements.
Given the magnitude of this discrepancy, some scientists theorize that our standard model of the universe’s evolution may be lacking some important information. Given that one approach examines the early universe and the other the current era, for instance, it is possible that the universe underwent a significant alteration over time. The “Hubble tension” is the term coined to describe this apparent mismatch. “.
Webb dips his toe in.
A powerful new tool that will allow humanity to see far into space is the James Webb Space Telescope, or JWST. The Hubble Telescope’s replacement, which was launched in 2021, has expanded our understanding of the universe by providing previously unobserved details about distant worlds, taking incredibly sharp pictures, and gathering vast amounts of data.
In order to measure the expansion rate of the universe, Freedman and her colleagues used the telescope to measure ten nearby galaxies.
They used three separate approaches to cross-check their findings. In the first, a Cepheid variable star—a kind of star whose brightness fluctuates predictably over time—is utilized. The second technique, dubbed the “Tip of the Red Giant Branch,” makes use of the fact that the brightness of low-mass stars has a maximum.
Using carbon stars—a class of star with uniform colors and brightnesses in the near-infrared spectrum—is the third and most recent technique. Throughout the same galaxies, the new analysis is the first to apply all three techniques at once.
In every instance, the values fell within the 67.4 km/s margin of error for the value obtained using the cosmic microwave background method.
According to Freedman, “having solid agreement from three very different kinds of stars is a strong indicator that we’re on the right track.”.
“More JWST observations will be essential for verifying or disproving the Hubble tension and evaluating the consequences for cosmology,” said study co-author Barry Madore, a visiting faculty member at the University of Chicago and member of the Carnegie Institution for Science.
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