Science

Solar neutrinos: messengers from within

Eyes are the mirrors of the soul: but what if you could gaze at the soul itself directly?

Here is an experiment which looks into the soul of the Sun and figures out what makes it shine! The Borexino experiment, which has been operating from Italy’s Gran Sasso Laboratory for the last seven years, has now come out with exciting results about the processes that keep the Sun going and glowing.

It is well known that the process that generates energy in the Sun involves pairs of protons combining to produce helium nuclei. In the process, neutrinos are also generated.

After prolonged effort, by suppressing the background signals, the Borexino experiment has enabled direct detection of the low-energy neutrinos produced in these nuclear reactions that initiate solar energy generation.

Early experiments to detect neutrinos noticed a gap between experiment and theory, with the total number of solar neutrinos detected falling between one-half to one-third of that predicted by theory.

This pointed to a gap either in the understanding of the Sun or the physics of the neutrinos. This problem caused many better and massive detectors to be built, including the Borexino detector and other experiments.

It is also known that neutrinos come in three types: the electron neutrino, muon neutrino and the tau neutrino. Those from the Sun’s core are the electron neutrinos. These can oscillate and change into the other types as they travel away from where they are born.

Other experiments explained the missing neutrinos by using the model where the neutrinos oscillate into other types (or flavours, namely the muon and tau neutrinos) before reaching the earth.

Borexino is in the news now for having detected the lowest energy neutrino branch which accounts for 90 per cent of the total flux. The results have been published today (August 28) in Nature.

Borexino is an international collaboration funded by the National Science Foundation, the Italian National Institute for Nuclear Physics (INFN), and other organisations from Germany, Russia, Poland and France.

Located deep beneath the Apennine Mountains, the Borexino instrument detects neutrinos as they interact with the electrons of an ultra-pure organic liquid scintillator at the centre of a large sphere surrounded by 1,000 tons of water.

Its great depth and many onion-like protective layers maintain the core as the most radiation-free medium on the planet.

This is the only detector on Earth capable of observing the entire spectrum of solar neutrinos simultaneously.


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Printable version | Oct 22, 2021 10:13:52 AM | https://www.thehindu.com/sci-tech/science/solar-neutrinos-messengers-from-within/article6357264.ece

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