Weighing neutrinos by watching galaxies dance ⚡ экспресс
Neutrinos are the most abundant particles in the universe, but their mass and the degree of asymmetry (the imbalance between particle and antiparticle concentrations) are still poorly known. For the first time, researchers used pairwise galaxy velocities (how fast they approach or recede from each other) from the Cosmicflows-4 catalog to place constraints on the total neutrino mass and the asymmetry parameter. An analysis within two independent cosmological models yielded consistent results: a neutrino mass around 0.3 eV and a robust detection of asymmetry (at the 7σ level). Galaxy motions thus become a new tool for neutrino physics—much like ripples on a pond revealing a fish beneath the surface.
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.