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Moon's reflections could shed light on mysterious cosmic particles

Elizabeth Howell, News Writer
Oct 2, 2014, 14:08 UTC

Sen—Scientists are planning to use the Moon to search for a rare kind of cosmic ray—an energetic particle that comes from parts unknown in the cosmos.

A science proposal for the Square Kilometre Array says that the Moon could serve as a reflector for these particles, providing more information about their origins.

The SKA is currently under construction in South Africa and Australia, with plans to make it operational by the mid 2020s. Billed as the world's largest radio telescope, it should be capable enough to pick up brief bursts of radio activity that the particles would generate on the lunar surface, the backers say.


Astronomers are hoping to use radio telescopes to probe cosmic rays on the Moon. Image credit: NRAO/AUI / Harry Morton (NRAO)

"With its large collecting area and high sensitivity, the SKA will be able to detect these signals using the visible lunar surface—millions of square kilometers—giving the researchers access to more data about UHE cosmic rays than they have ever had before," stated the University of Southampton, where research fellow Justin Bray leads the proposal.

“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," added Bray in the press release. "If we can make this work, it should give us our best chance yet to figure out where they’re coming from."

The ultra-high energy cosmic rays the scientists seek not only have mysterious origins, but an unknown source of energy. What makes them harder to find is how rare they are; on Earth, they are only found at the rate of less than one particle per square kilometre per century.


An artist's impression of the Square Kilometre Array. Image credit: SKA Organisation

The proposal suggests that researchers would be able to find 165 examples of this type of cosmic ray annually from the Moon, which is far more than the 15 cosmic rays on the Moon that astronomers can currently find every year.

Since SKA is such a headline project, it is bound to attract a lot of competing proposals from astronomers interested in its capabilities. Observing time has yet to be fully allocated for the radio array, and proposals must be reviewed by SKA officials before it is decided whether to accept them.

The conference presentation for this proposal, called "Lunar detection of ultra-high-energy cosmic rays and neutrinos", is available on the prepublishing site Arxiv.