A New Experiment in the Hunt for Neutrinos
Astronomers Suspect High Energy Neutrinos Could be Detected on Moon
Aug 6, 2009
The term "neutrino" means "small, neutral one" and is attributed to its relatively diminutive size and its lack of any electrical charge. Scientists classify neutrinos as fundamental particles that pass easily through matter, only occasionally colliding with atomic nuclei. Until now, the only extraterrestrial neutrinos that have been found were forged in the sun and in one nearby supernova called 1987A.
High Energy Neutrinos
Astronomers believe that the universe is full of neutrinos with higher energy than those found in the local solar system. These neutrinos are believed to be produced by cosmic accelerators that enable charged particles to reach energies about 100 million times as high as those generated in the most powerful particle accelerators on Earth.
Why are Neutrinos Difficult to Detect?
Neutrinos are known to have the ability to pass through ordinary matter almost undisturbed. As a result, they are extremely difficult to detect. They are created as a result of certain types of radioactive decay or nuclear reactions such as those that take place in the Sun, nuclear reactors or when cosmic rays collide with atomic nuclei. Most neutrinos passing through the Earth come from the Sun, it is believed that more than 50 trillion solar electron neutrinos pass through the human body every second.
Neutrino Activity on the Moon
Because neutrinos rarely interact with matter, large expanses of material are needed to catch as many of them as possible. Detectors are designed to look for flashes of light that are produced when speeding neutrinos slam into atoms, creating an explosion of particles that generate light as they pass through a medium. These high-energy neutrinos that collide with lunar soil atoms should produce nanoseconds-long bursts of radio waves that can move through the lunar surface for tens or hundreds of meters.
Detecting High Energy Neutrino Collisions on the Moon
A radio telescope aimed toward the edge of the moon could theoretically detect these ultra-high energy radio emissions. However, neutrino collisions at ultra-high energies are rare; astronomers might expect to see only a few in a month. In addition, radio telescopes must weed out the background interference signs that must be excluded to get confirmable data.
Rachel Courtland from New Scientist notes that because they are not charged, neutrinos are not deflected by magnetic fields that weave through space and bend the paths of charged cosmic rays. As a result, this property could allow astronomers to track neutrinos back to their source. "They will tell us what the highest-energy accelerators in the universe have done throughout history back to the big bang," says Peter Gorham of the University of Hawaii at Manoa.
Terrestrial Neutrino Experiments
Gorham also runs a neutrino detection experiment called ANITA, which is a balloon detector system that circles the South Pole in search of radio signals made by neutrino collisions. Radio waves can travel farther in ice than in the lunar soil, also producing stronger signals when detected. If present moon experiments do not find neutrinos, researchers hope their developments allow for neutrino searches with larger, more sensitive radio arrays. One proposed project is the Square Kilometer Array, which could also detect the neutrino collisions that the ANITA is hunting for.
Source:
Courtland, Rachel. "Moon used as giant particle detector - space - 05 August 2009 - New Scientist.". NewScientist.com, 05 Aug. 2009. Viewed 06 Aug. 2009.
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