Scientists have discovered that ultraheavy atomic nuclei could explain some of the highest-energy cosmic rays ever observed. The particles may come from extreme events such as neutron-star mergers and collapsing massive stars.
Scientists may have uncovered a new clue behind the origin of the most energetic particles ever detected in the universe.
Ultrahigh-energy cosmic rays are particles from space that slam into Earth with energies far beyond anything produced by human-made particle accelerators. One of the most extreme examples is the “Amaterasu particle,” detected in Utah by the Telescope Array in 2021 and named after the Japanese sun goddess. Its energy rivals that of the famous “Oh-My-God particle” discovered in 1991, but scientists still do not know exactly what it was or where it came from.
New research from Penn State scientists, published in Physical Review Letters, suggests that some of these record-breaking cosmic rays may be made of atomic nuclei heavier than iron. Atomic nuclei are the dense centers of atoms composed of protons and neutrons, containing nearly all of an atom’s mass.
Ultraheavy Nuclei May Explain Extreme Cosmic Rays
The researchers found that these ultraheavy nuclei may lose energy more slowly than protons or lighter nuclei while traveling through intergalactic space. That could allow them to cross enormous cosmic distances and still reach Earth with exceptionally high energies. The work involved scientists from the Yukawa Institute for Theoretical Physics in Japan, Virginia Tech, and several other institutions and could help narrow the search for the cosmic environments capable of accelerating such particles.
“Ultrahigh-energy cosmic rays can only be accelerated by some of the most powerful sources in the universe,” said Kohta Murase, professor of physics and of astronomy and astrophysics in the Penn State Eberly College of Science and the leader of the research team. “When we detect individual cosmic-ray particles such as the Amaterasu particle here on Earth, we can often use their energies, arrival directions, and expected magnetic deflections to infer their possible cosmic sources.”
