Scientists in India observed the highest-voltage thunderstorm ever documented with the help of a subatomic particle you might not hear much about: the muon.

The researchers operate the GRAPES-3 telescope, which measures muons, particles that are similar to electrons but heavier. Specifically, the Gamma Ray Astronomy at PeV EnergieS Phase-3 (GRAPES-3) muon telescope measures high-energy particles from outer space called cosmic rays. It typically picks up 2.5 million muons each minute, mapped on a 13-by-13 grid across the sky. But during thunderstorms, it experiences quick changes to the amount of muons it receives. The GRAPES-3 researchers added electric field monitors to the experiment, and devised a way to turn these muon fluctuations into measurements of the voltage of passing storms.