High-energy particles whizz through the Universe, and past Earth, every second of every day. While most of these particles (neutrinos, quarks, etc.) can be detected to one degree or another, one subatomic actor, Ultra-High-Energy cosmic rays (UHECR), has been exceedingly difficult to uncover.
First discovered by Dr. John Linsley & Livio Scarsi in 1962, UHECRs are remarkable in that they contain an amazing amount of energy for their size. In fact, during a survey at the Dugway Proving Ground in 1991 researchers were astonished to discover a UHECR over 10 million times more energetic than any other particle ever detected. Aptly named the “Oh-My-God particle”, the quantum specimen packed the energy equivalent of a 142g (5oz) baseball travelling 100 km/h (60 mph).
Though it may appear that detecting a particle with such a high energy signature would make a researcher’s job easier, that isn’t the case with UHECRs. According to physicists one of the most confounding issues surround the cosmic rays are their scarcity, the particle providing just one collision per km2 per century.
In order to expand the statistical chance of observing a UHECR, Southampton physicist Dr. Justin Bray has proposed using the Square Kilometer Array (SKA) radio telescope and the Moon’s visible surface to study the elusive particle.
“Cosmic rays at these energies are so rare that you need an enormous detector to collect a significant number of them - but the moon dwarfs any particle detector that has been built so far. If we can make this work, it should give us our best chance yet to figure out where they’re coming from,” said Bray.
In theory, the Moon could act as a particle detector using its 19M km2 (7.3M mi2) Earth-facing surface as a reflector for UHECRs. After having collided with the lunar surface the particles would emit radio waves which could be detected by the SKA array. Once ensnared by the radio telescope researchers would have valuable data from which they could tease out the intricacies of the elusive UHECR.
With the SKA set to come online sometime in the early 2020s it may be a while before researchers unlock the secrets of UHECRs. However, the wait should be well worth it. Physicists currently believe the particles could play a role or be linked to the Penrose Effect, gamma ray bursts, hypernovae and even dark energy. Either proving or disproving those relationships would be a huge accomplishment towards understanding the fundamental nature of the Universe, and well worth repurposing the Moon.
Image Courtesy of University of Southhampton