Ghostly Milky Way Neutrinos Finally Measured by Astronomers

For the first time, astronomers have measured how many neutrinos from the Milky Way reach Earth. These ghostly particles, produced by stars beyond our Sun, stream through the planet in vast numbers. The findings reveal their origins and energy levels in unprecedented detail.

The Milky Way's thin disk, packed with young, massive stars, is the main source of these neutrinos. This region's high stellar activity ensures a steady flow, with the current influx at its peak due to ongoing star formation. Most neutrinos detected have energies around 0.5 MeV, primarily coming from stars larger than the Sun.

At lower energies, around 0.01 MeV, roughly 1 billion neutrinos pass through every square centimetre of Earth—and our bodies—each second. At slightly higher energies near 0.1 MeV, the number drops to about 100 billion per square centimetre. Even at energies above 1 MeV, between 100,000 and 1 million neutrinos still arrive per square centimetre every second.

The particles mostly travel from distances of 16,000 to 32,000 light-years, with the galactic centre acting as a major source. However, their overall influx remains five orders of magnitude weaker than neutrinos from the Sun or high-energy cosmic events. Earlier detections by the IceCube Neutrino Observatory at the South Pole had already identified high-energy neutrinos from the Milky Way's galactic plane, using ice-based detection methods.

The precise mapping of these stellar neutrinos provides a clearer picture of their distribution and energy ranges. While their numbers are dwarfed by solar or cosmic neutrinos, the data confirms the Milky Way's thin disk as their dominant origin. This research marks a step forward in understanding the galaxy's invisible particle streams.