The James Webb Space Telescope has measured the rate of expansion of the universe, and the results are not good news for the biggest crisis in cosmology.
This finding is consistent with measurements made by the Hubble Space Telescope. This means Hubble’s data is error-free, but it’s still a dead end.
The discrepancy between different measurement methods, known as the Hubble tension, remains, so we must rely on other methods to find out how fast the universe is expanding.
Although the universe around us appears to be unchanged, everything we see is actually moving away from us at an incredible rate known as the Hubble constant (H0). It’s unclear exactly how fast H0 is. This is because different measurement methods yield different results.
One way is to look at relics of the early universe, such as leftover light from the cosmic microwave background or sound waves frozen in time.
Another method is to measure the distance to an object with a known unique brightness, such as a Type Ia supernova. Cepheid variable starThe light fluctuates regularly in conjunction with the original brightness.
The first method tends to return an expansion rate of about 67 kilometers per second per megaparsec. The second is about 73 kilometers per second per megaparsec. The discrepancy between the two is known as the Hubble tension.
These measurements were performed repeatedly, greatly reducing the potential for error in each estimate. However, there is still the possibility that there is something misleading about at least some of the data. Especially since some of the best data on Cepheid variable stars comes from a single source: the Hubble Space Telescope.
”[Cepheid variables] is the gold standard tool for measuring the distances of galaxies more than 100 million light-years away and is an important step in determining the Hubble constant. Unfortunately, the stars in our galaxy are packed together in a small space from our distant vantage point, so we lack the resolution to separate them from their neighbors in our line of sight. This often happens. ” Astrophysicist Adam Rees explains: from the Space Telescope Science Institute (STScI) and Johns Hopkins University.
“The main justification for building the Hubble Space Telescope was to solve this problem…The Hubble Space Telescope has better visibility than any ground-based telescope because it is unaffected by the blurring of Earth’s atmosphere. It has wavelength resolution. As a result, it is able to identify individual Cepheid variable stars, which reside in galaxies more than 100 million light-years away and measure the time intervals over which their brightness changes. ”
To cut dust that blocks light near the optical system These observations need to be made in the near-infrared, a part of the electromagnetic spectrum that Hubble is not very good at. This meant that some uncertainty remained about the data Hubble obtained.
JWST, on the other hand, is a powerful infrared telescope, and the data it collects does not have the same limitations.
Reese and his team first set up JWST at a galaxy with known distances and calibrated the telescope to the luminosities of Cepheid variable stars. They then observed Cepheids in other galaxies. In total, JWST collected his 320 Cepheid observations, significantly reducing the noise found in Hubble observations.
Despite the noisy Hubble data, the data for determining distances were still consistent with JWST observations. This means that calculation of H0 based on Hubble data cannot be ruled out. 73 kilometers per second per megaparsec persists for some time, and human error cannot explain the Hubble tension, at least in this case.
We still don’t know what’s causing the tension. One of the leading candidates is dark energy. This appears to be a mysterious, unidentified but fundamental force. apply negative pressure This is what is accelerating the expansion of the universe. New JWST measurements may bring us a little closer to the answer.
“With Webb’s confirmation of Hubble’s measurements, Webb’s measurements provide the strongest evidence that systematic errors in Hubble’s Cepheid photometry do not play a significant role in the current Hubble tension. .” Reese says.
“That leaves more interesting possibilities on the table and deepens the mystery of the tension.”
The results were accepted by astrophysical journaland is available in arXiv.