Cosmic rays are tiny, very rare particles that travel from space into Earth’s atmosphere. These rays have more energy than any other known particles in the universe. For decades, scientists have wondered where these ultra-high-energy rays come from. Now, they seem to have found the answer. Scientists at the Pierre Auger Observatory in Argentina have found the first solid evidence that these energetic particles come from super massive black holes in galaxies near ours.

For the new study, the observatory recorded 27 ultra-high-energy cosmic rays. Results showed that 20 of those particles came from points in the sky where galaxies that contain massive black holes are already known to be. The link is too strong to be a coincidence, the researchers say.

How are cosmic rays produced?

The researchers suggest that the cosmic rays are coming from that area of a galaxy known as the active galactic nucleus (called AGN). How do AGNs produce such high-energy particles? Scientists have discovered that black holes inside AGNs feed on swirling disks of gas and dust. As the material spirals in, they probably heat up and spit out radiation with lots of energy.

The Auger observatory, at which the discovery was made, is an enormous one. Its objective is to catch as many cosmic rays as possible. Since these rays are hard to catch, the observatory sprawls out over 3,000 square kilometres. After all, one square kilometre of Earth’s upper atmosphere gets hit by cosmic rays just once every 100 years or so.