Cosmic Clocks Diverge: A New Mystery of the Universe's Expansion ⚡ экспресс
The problem of discrepancy in Hubble constant measurements remains acute. A re-analysis of the two-step distance ladder was performed, based exclusively on Cepheid periods and apparent magnitudes, with anchor distances in the Milky Way, Large Magellanic Cloud, NGC 4258, and redshifts of host galaxies. The latest carefully selected data from the SH0ES collaboration were used, where Cepheid host galaxies also contain Type Ia supernovae. Two key improvements were implemented: rigorous selection modeling and the modern Manticore-Local peculiar velocity field model, built on the BORG Bayesian algorithm. Assuming the sample is limited by supernova brightness, a value of H0 = 71.1 ± 1.4 km/s/Mpc was obtained; alternative selection criteria could raise the estimate by one standard deviation. The posterior distribution has a lower central value and 41% smaller uncertainty compared to the previous analysis of the same data. The result is 1.3σ below the SH0ES value (73.2 ± 0.9 km/s/Mpc) and diverges from the latest cosmic microwave background data within the standard cosmological model at the 2.8σ level.
Measuring the expansion of the Universe is like checking the time on two perfect clocks: one set by the ancient light of the cosmic microwave background, the other by stars and supernovae. And the more precisely we compare them, the more their readings diverge. Now, a new 'clock' using only pulsating Cepheid stars has added a third, even more unexpected result.
Astronomers carefully accounted for the motion of galaxies relative to each other and obtained a Hubble constant of 71.1 (km/s)/Mpc. This is lower than the previous standard (73.2 from Adam Riess), but the discrepancy with the 'relic radiation' clock has grown to a level where chance is almost ruled out (less than 0.5%). Contrary to hopes, cleaning up the mechanism did not synchronize the clocks but only highlighted the fault.
In 1929, Edwin Hubble using the same Cepheids calculated 500 (km/s)/Mpc — it turned out he confused two types of these stars. We no longer confuse them, but the divergence hints that in the very mechanism of the cosmic clocks — the standard model — there may be some missing gears.
🎯 Edwin Hubble's first measurement in 1929 gave about 500 km/s per megaparsec — seven times larger than today's, because he didn't know about the two types of Cepheids.