Weighing neutrinos by watching galaxies dance ⚡ экспресс
Neutrinos are among the most abundant fermions in the universe, yet their masses and chemical potentials remain elusive. For the first time, constraints on the total neutrino mass Mν and the asymmetry parameter η² have been derived from an analysis of mean pairwise peculiar velocities of galaxies in both quasi-linear and nonlinear regimes. A pipeline was developed that connects neutrino properties to pairwise velocity predictions and was applied to data from the Cosmicflows-4 catalog. The analysis was performed within two cosmological frameworks: one with parameters from the cosmic microwave background (CMB) and one from the local distance ladder. Consistent constraints were obtained: in the CMB framework, Mν = 0.24+0.34–0.18 eV, η² = 2.14+0.30–0.32, with a detection of nonzero asymmetry at the 7σ level; in the local framework, Mν = 0.37+0.34–0.26 eV, η² = 2.4+2.1–1.6. The results are in agreement with previous work from CMB power spectra and demonstrate that galaxy pairwise velocities serve as an independent and sensitive probe of neutrino properties, opening a new avenue for testing neutrino physics in large-scale structure observations.
Neutrinos are the most abundant massive particles in the universe. Trillions of them pass through us every second, yet they leave barely a trace. Their collective gravity, though tiny, can influence the motion of entire galaxies. Think of two people approaching each other on a busy street; invisible passersby alter their speed. Similarly, for galaxy pairs, neutrinos act as those unseen passersby, subtly distorting their motion. Comparing with computer simulations yielded a total mass of about 0.24 electronvolts and, more surprisingly, exposed an imbalance: more neutrinos than antineutrinos. This skew contradicts the simplest versions of the Standard Model and calls for new physics.
Such an excess of neutrinos in the early universe could have been a hidden factor steering the growth of galaxy clusters. The method opens a way to study neutrino properties without giant accelerators – simply by watching the dance of galaxies.
🎯 A single neutrino is a million times lighter than an electron, but there are a billion times more neutrinos than atoms in the universe.