The second most powerful cosmic ray ever discovered may have come from a galaxy

Amaterasu is an ultra-high-energy cosmic ray discovered in 2021 by the Telescope Array Project in the United States. Its energy was impressive, and it is the second most powerful cosmic ray ever detected. However, its origin remains a mystery.

Some researchers have suggested that this cosmic ray came from the Local Void, a region of space near the Milky Way with few galaxies. However, this hypothesis is surprising, because this cosmic ray would have been accelerated by various structures in the universe, such as black holes or supernovae.

A study recently published in The Astrophysical Journal highlights another origin. Indeed, M82 is a very active spiral galaxy located about 12 million light-years from Earth. It has extremely powerful galactic winds, black holes, and astronomers have also observed supernovae. In other words, this could be the source of the Amaterasu particle.

But according to this study, other galaxies could also be the cause of this cosmic ray, such as NGC 6946 and NGC 2403. However, they are much less active than M82. Thus, new observations will be needed, particularly with the help of the Telescope Array Project in the United States and the Pierre Auger Observatory in Argentina. Indeed, improvements will be made on these devices to unravel this mystery.