Astronomers, a race of stellar priests-cum-poets of sorts, use electromagnetic radiation - such as light or radio waves - that is emitted by those distant worlds in order to investigate the mysteries of the universe and to explore the evolution of stars and planets. However, there are parts of the universe that are opaque to optical or radio telescopy. For example, the nuclei of stars, the dense centres of galaxies or the early universe when light did not yet exist.

The experimental confirmation of the mysterious neutrino particle in 1956 ushered in a new era in astronomy - called neutrino astronomy - that can boldly go where other astronomies cannot and see things no optical or radio telescope can.

Neutrinos (not to be confused with neutrons) were first theorised to exist in 1930 by the famous physicist Wolfgang Pauli. They are tiny particles that result from nuclear reactions, such as the ones taking place in the Sun or inside a nuclear reactor. Unlike electrons (which are negatively charged), neutrinos have no electric charge and are virtually massless. Thus, they pass through matter unhindered - every second 50 trillion of those ghostly things pass through your body without you noticing it.

The bonus of being like a ghost is that you can travel through anything, anywhere, anytime. Compare that with photons, the particles of light. Photons produced inside the core of the Sun interact with mass and take 40,000 years to reach its outer surface and become visible by our optical telescopes. This is because photons interact with the electromagnetic forces inside the core of the Sun, which impede their transmission. Neutrinos, having no charge and interacting with nothing, travel from the core to the surface almost instantly.

A similar phenomenon occurs during the final stages in the lifetime of a big star. When such a massive star burns out, it implodes and then violently explodes all its matter and energy into space. The phenomenon is called a supernova and is one of the most spectacular and amazing events in the universe. In 1987 detection of a massive neutrino storm foretold a supernova explosion 18 hours before the light from the explosion arrived at Earth.

Let us return for a moment back to our imaginary telescope. Modern astronomy tells us that all the stars and the galaxies out there, all ordinary matter as it is called, account for only four percent of the universe. Of the rest, 22 percent is made up of the mysterious dark matter and 74 percent of the even more mysterious dark energy. Dark matter is responsible for the way galaxies are clustered together. It gives the universe its shape and is made up from weakly interacting particles of matter that are still unknown. Neutrinos may account at least for a part of the missing dark matter.

With so many cosmic mysteries to solve, the scientific interest in neutrinos is great. Since the late 1950s, many scientists and engineers have tried to develop machines that could detect them. This is no easy feat. If we wanted to block half the typical neutrinos that emanate from our Sun, for example, we would need a sphere of water around the Sun with a radius of 10 light years.

Source: Athens News