Amazing stuff!
"New observations from the James Webb Space Telescope suggest that a new feature in the universe—not a flaw in telescope measurements—may be behind the decadelong mystery of why the universe is expanding faster today than it did in its infancy billions of years ago.
The new data confirms Hubble Space Telescope measurements of distances between nearby stars and galaxies, offering a crucial cross-check to address the mismatch in measurements of the universe's mysterious expansion. Known as the Hubble tension, the discrepancy remains unexplained even by the best cosmology models. ...
"The discrepancy between the observed expansion rate of the universe and the predictions of the standard model suggests that our understanding of the universe may be incomplete," said Nobel laureate and lead author Adam Riess, a Bloomberg ...
"The discrepancy between the observed expansion rate of the universe and the predictions of the standard model suggests that our understanding of the universe may be incomplete," said Nobel laureate and lead author Adam Riess, a Bloomberg ...
Observations from both telescopes aligned closely, revealing that Hubble's measurements are accurate and ruling out an inaccuracy large enough to attribute the tension to an error by Hubble. ...
While the standard model yields a Hubble constant of about 67-68 kilometers per second per megaparsec, measurements based on telescope observations regularly give a higher value of 70 to 76, with a mean of 73 km/s/Mpc. This mismatch has perplexed cosmologists for more than a decade because a 5-6 km/s/Mpc difference is too large to be explained simply by flaws in measurement or observational technique. ...
Since Webb's new data rules out significant biases in Hubble's measurements, the Hubble tension may stem from unknown factors or gaps in cosmologists' understanding of physics yet to be discovered, Riess' team reports. ..."
From the abstract:
"We cross-check the Hubble Space Telescope (HST) Cepheid/Type Ia supernova (SN Ia) distance ladder, which yields the most precise local H0, against early James Webb Space Telescope (JWST) subsamples (∼1/4 of the HST sample) from SH0ES and CCHP, calibrated only with NGC 4258. We find HST Cepheid distances agree well (∼1σ) with all combinations of methods, samples, and telescopes. The comparisons explicitly include the measurement uncertainty of each method in NGC 4258, an oft-neglected but dominant term. Mean differences are ∼0.03 mag, far smaller than the 0.18 mag "Hubble tension." Combining all measures produces the strongest constraint yet on the linearity of HST Cepheid distances, 0.994 ±0.010, ruling out distance-dependent bias or offset as the source of the tension at ∼7σ. However, current JWST subsamples produce large sampling differences in H0 whose size and direction we can directly estimate from the full HST set. We show that ΔH0 ∼ 2.5 km s−1 Mpc−1 between the CCHP JWST program and the full HST sample is entirely consistent with differences in sample selection. We combine all JWST samples into a new distance-limited set of 16 SNe Ia at D ≤ 25 Mpc. Using JWST Cepheids, JAGB, and tip of the red giant branch, we find 73.4 ± 2.1, 72.2 ± 2.2, and 72.1 ± 2.2 km s−1 Mpc−1, respectively. Explicitly accounting for common supernovae, the three-method JWST result is H0 = 72.6 ± 2.0, similar to H0 = 72.8 expected from HST Cepheids in the same galaxies. The small JWST sample trivially lowers the Hubble tension significance due to small-sample statistics and is not yet competitive with the HST set (42 SNe Ia and 4 anchors), which yields 73.2 ± 0.9. Still, the joint JWST sample provides important cross-checks that the HST data pass."
JWST Validates HST Distance Measurements: Selection of Supernova Subsample Explains Differences in JWST Estimates of Local H0 (open access)
Figure 4. Anchors and SN Ia hosts selected to cross-check HST and JWST distances from the full HST sample of four anchors and 42 SNe Ia.
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