The mass of the elusive neutrino is less than 0.28 electronvolts — the lowest upper limit predicted so far — according to Shaun Thomas and his colleagues at University College London.
Neutrinos are abundant in the Universe but are difficult to detect and measure directly as they rarely interact with matter. To predict the particle's mass, the researchers constructed a map of the density distribution of 700,000 galaxies using data from the Sloan Digital Sky Survey. Neutrinos can suppress the growth of galaxies, and that suppression is greater for larger neutrinos. Using this correlation, the researchers could infer an upper bound for neutrino mass.