Researchers propose that ultraheavy atomic nuclei may explain the origins of the highest-energy cosmic rays ever observed [1].
This theory addresses a long-standing mystery in astrophysics regarding how particles maintain extreme energy levels while traveling across the vacuum of space. If these particles are ultraheavy, they could travel further without degrading, potentially revealing the locations of the most violent events in the universe.
The research focuses on the behavior of cosmic messengers and their ability to withstand intergalactic travel [1]. The researchers said ultraheavy nuclei lose energy more slowly than lighter particles during their journey [2]. This characteristic allows them to survive vast distances and reach Earth while still possessing extreme energies [1].
One primary example of this phenomenon is the Amaterasu particle, which was detected in 2021 [1]. The particle was captured by the Telescope Array observatory located in Utah, U.S. [2]. The detection of such a high-energy particle challenged previous understandings of cosmic ray propagation, specifically how a particle could arrive from a region of space that appeared void of potential sources.
By proposing that these messengers are composed of ultraheavy nuclei, scientists said they can better account for the particle's survival and its energy profile upon arrival [2]. The Telescope Array continues to monitor the skies for similar events to determine if this composition is a common trait among the most energetic rays [1].
This shift in theoretical approach suggests that the composition of cosmic rays is more diverse than previously assumed. While lighter elements like protons have been the primary focus of study, the inclusion of ultraheavy nuclei provides a new mechanism for particles to traverse the cosmos without losing their signature energy [2].
“Ultraheavy nuclei lose energy more slowly during intergalactic travel.”
The proposal that ultraheavy nuclei drive the most energetic cosmic rays suggests that the 'GZK limit'—the theoretical energy cap for cosmic rays traveling long distances—may be bypassed by heavier particles. This allows astronomers to look further into the distant universe for sources of these particles, potentially identifying new classes of extreme astrophysical objects that were previously thought to be too far away to be detected.
