Unite supernova catalogue challenges constant dark energy model

September 11, 2026 at 07:30 PM2 min

This digest was compiled by AI from multiple sources — links to the originals are below.

A new catalogue of 2,884 likely Type Ia supernovae, called Unite, has made the cosmological constant assumption harder to fit alongside other major measurements. The work, submitted on 4 September 2026 and revised on 9 September, has not completed peer review. The stronger hint of evolving dark energy appears only after Unite is combined with galaxy-based distance measurements and the cosmic microwave background.

Key Facts

The Unite catalogue combines 2,884 likely Type Ia supernovae from Pantheon+ and the Dark Energy Survey's five-year sample.
The preprint was submitted on 4 September 2026 and revised on 9 September 2026.
The supernova catalogue by itself remains consistent with no time evolution in dark energy.
The stronger hint of evolving dark energy appears only after combining Unite with galaxy-based distance measurements and the cosmic microwave background.
The team recalculated host-galaxy stellar masses for more than 98 per cent of the sample.

Catalogue Construction

Ryan Camilleri and colleagues combined the Pantheon+ compilation with the Dark Energy Survey's five-year supernova sample, then reanalysed the observations through a more consistent pipeline. Pantheon+ assembled 1,701 light curves from 1,550 unique, spectroscopically confirmed supernovae observed by many telescopes, reaching redshift 2.26. DES-SN5YR supplied a large, relatively homogeneous high-redshift sample from the Dark Energy Survey. Unite resolves overlaps and applies common choices for light-curve modelling, sample selection and bias correction. It also adopts an updated cross-calibration between instruments and requires Dark Energy Survey candidates to have a Type Ia probability above 80 per cent.

Cosmological Implications

The standard cosmological model treats dark energy as a constant density that does not change as space expands. The Unite catalogue has made that assumption harder to fit alongside several other major measurements. The supernova catalogue by itself remains consistent with no time evolution in dark energy. The stronger hint appears only after Unite is combined with galaxy-based distance measurements and the cosmic microwave background. The companion host-mass analysis found that redshift-dependent differences of only about 0.01 magnitude can shift cosmological constraints appreciably.