A Strong Progenitor Age Bias in Supernova Cosmology

Thread starter PeterDonis
Start date Nov 6, 2025

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The recent paper highlights a significant correlation between the luminosity of Type Ia supernovae and the age of their progenitor galaxies, suggesting a systematic bias in supernova cosmology that has been largely uncorrected by existing methods. This bias affects the interpretation of supernova data, leading to discrepancies with cosmic microwave background (CMB) measurements. After adjusting for progenitor age, the supernova data aligns more closely with the cold dark matter model proposed by the Dark Energy Spectroscopic Instrument (DESI). The findings imply a decelerating universe rather than an accelerating one, challenging previous conclusions about dark energy. Overall, this research calls into question the standardization of Type Ia supernovae as reliable distance indicators in cosmology.

Tuesday, 12:10 AM

eloheim

PeterDonis said:

That shouldn't be possible with a cosmological constant, because the energy density of matter and radiation can only decrease with expansion, so once the universe has expanded to the point where the cosmological constant dominates, it should keep dominating (i.e., expansion should keep accelerating) forever after that.

Ah, thank you! That was basically my guess but I didn't want to assume.

PeterDonis said:

In other words, IMO that pattern of accelerated expansion starting 7 bya and then stopping 2 bya is a reason to doubt that the findings of this paper are actually valid.

Yeah that's what I was getting at. Hopefully we'll get some interesting responses/rebuttals in the coming months.