Universe's expansion rate refined using supernova 'twins' express
Type Ia supernovae are like light bulbs of a fixed wattage: the dimmer the light, the farther the source. Such supernovae serve as distance markers to remote galaxies. But cosmic dust, like a dirty window, dims and reddens the light, messing up the calculations. Astronomers led by Adam Riess sidestepped the problem: they compared only 'twins'—supernovae with identical properties, whose light traveled through similarly dusty regions. It's like gauging distance by lamps hidden in identical lampshades. The new data yield a universe expansion rate of about 72.4 km/s per megaparsec (that's 3.26 million light-years). That's noticeably faster than the ancient light from the Big Bang predicts. The discrepancy, known as the 'Hubble tension', has now grown even stronger.
Original abstract
as written by the authors arXiv:2512.02391
We have applied our approach of using ''SNe Ia twins''in the Hubble flow to obtain distances to SNe Ia at z $$>$$ 0.015 and derive H$$_{0}$$. Our results, taking a single step between the low z domain and the Hubble flow, validate the three rung classical method. We find, however, that the full compilation of distances, both in Pantheon+ and in the Carnegie-Chicago Hubble Program (CCHP), contain some inaccurate values in the colors due to an underestimate of reddening by dust, or due to the adoption of not well--defined light curve declines.This produces odd individual values for H$$_{0}$$ from single Type Ia SNe (SNe Ia). Our sample of carefully addressed SNe Ia in the Hubble flow contains a dozen supernovae, for which the distances are determined with high accuracy. Three of these SNe Ia are of the Broad Line subtype and can be compared with SN 1989B in M66, a host galaxy with a unique convergence of the Cepheid distance determination and the Tip of the Red Giant Branch stars (TRGB) determination by the CCHP group. There is, as well, a very good agreement on the distances to NGC 7250 and NGC 5643 between those derived with Cepheids by SH0ES and those derived with the use of J-Asymptotic Giant Branch stars(JAGB stars) by the CCHP, which makes them very good anchors. The sample of 12 SNe Ia gives a value of H$$_{0}$$ $$=$$ 72.56 $$\pm$$ 1.54 (stat) $$\pm$$ 1.33(sys) km s$$^{-1}$$ Mpc $$^{-1}$$,when anchored in Cepheids, and of H$$_{0}$$ $$=$$ 72.20 $$\pm$$ 1.53 (stat) $$\pm$$ 1.33 (sys) km s$$^{-1}$$ Mpc $$^{-1}$$,when anchored in JAGBs by the CCHP.We take a mean of the two values of H$$_{0}$$ as derived by the Cepheids and by JAGB (from the CCHP) and obtain H$$_{0}$$ $$=$$ 72.38 $$\pm$$ 1.54(stat) $$\pm$$ 1.33(sys) km s$$^{-1}$$ Mpc $$^{-1}$$. Our findings confirm that the Hubble tension is real.
It was precisely with type Ia supernovae that the accelerating expansion of the universe was discovered in 1998—a Nobel Prize-winning breakthrough.
Confirmation of the Hubble tension makes sci-fi scenarios where physical laws evolve just a little less fictional.