We finally solved a 20-year mystery about why ancient stardust is so weird by measuring a rare radioactive atom.
March 19, 2026
Original Paper
First $^{94}$Nb($n,γ$) Measurement: Constraining the Nucleosynthetic Origin of $^{94}$Mo in Presolar Grains
arXiv · 2603.17646
The Takeaway
Tiny grains of stardust found in meteorites were born from dying stars billions of years ago, but their chemical makeup didn't match scientific models of how stars forge elements. By finally measuring how a specific radioactive version of Niobium captures neutrons, physicists found the 'missing link' that makes the stardust data and stellar theory perfectly align.
From the abstract
Isotopic measurements of presolar silicon carbide grains from dying stars have revealed a puzzling overabundance of $^{94}$Mo that stellar nucleosynthesis models have failed to reproduce for two decades. This discrepancy challenged our understanding of the slow neutron-capture process ($s$-process) that forges approximately half of the elements heavier than iron. The key uncertainty lies at $^{94}$Nb, a radiactive branching point where competition between neutron capture and beta decay governs t