Physics: ‘Ghost particles’ emitted by the SUN shed light as massive stars shine



Elusive ‘ghost particles’ formed deep in the sun have been detected for the first time, helping to shed the reactions that make massive stars shine.

Researchers were able to capture evidence of these particles as they passed through a special detector buried under a mountain near the town of L’Aquila, Italy.

These rare emissions – which have traveled 90 million miles to reach us – are produced in certain nuclear reactions that account for less than a percentage of the sun’s energy.

These reactions are however thought to be more dominant in larger stars – and may help to explain their formation and evolution.

Elusive ‘ghost particles’ formed deep in the sun have been detected for the first time, helping to shed the reactions that make massive stars shine.  Researchers were able to capture evidence of these particles as they passed through a special detector buried under a mountain near the town of L'Aquila, Italy.  The image is the core of the Borexino detector

Elusive ‘ghost particles’ formed deep in the sun have been detected for the first time, helping to shed the reactions that make massive stars shine. Researchers were able to capture evidence of these particles as they passed through a special detector buried under a mountain near the town of L’Aquila, Italy. The image is the core of the Borexino detector

“Now we finally have the first, ground-breaking, experimental confirmation of how stars heavier than the sun shine,” said paper author and astroparticle physicist Gianpaolo Bellini of the University of Milan.

Stars are powered by the fusion of hydrogen into helium, which can happen through two different processes – the first is the so-called proton-proton chain, which involves only isotopes of hydrogen and helium. This is dominant in stars like the sun.

In larger stars, however, the so-called carbon-nitrogen-oxygen (CNO) cycle – in which the three elements help to catalyze the nuclear reactions – becomes a more significant energy source. It also ghostly releases particles called neutrinos.

These are nearly masculine – and are capable of passing through ordinary matter without giving an indication of their presence.

Physicists wanted to study the sun’s emissions, because they would better understand how the CNO cycle works in our stars, as a larger star – where the process is dominant – burns their nuclear fuel.

To detect the sun’s CNO neutrino emissions, physicists used the so-called ‘Borexino detector’ – a 55-foot-high, layered, bulb-like machine that contained in its heart a spherical tank called a ‘scintillator’ filled with 278 Tons of a special liquid.

When neutrinos pass through the liquid, they can interact with the electrons – releasing tiny flashes whose brightness indicates the energy of the neutrino, with which the CNO cycle is formed at a deeper end.

These are picked up by camera-like sensors and analyzed by powerful hardware.

To ensure that the detector receives only the rare neutrino signals – and is not absorbed by cosmic radiation – the Berexina experiment is buried underground and further discharged by being cocooned into a water tank.

“This is the culmination of a thirty year long effort begun in 1990 – and of more than ten years of Borexino’s discoveries in the physics of the sun, neutrinos and finally stars,” said Professor Bellini.

According to physicist Gioacchino Ranucci, also from Milan, the success of the experiment should be credited to the ‘unprecedented purity’ of the solution.

The detection of the CNO neutrinos has revealed how much of the sun is made of the elements carbon, nitrogen and oxygen.

To detect the CNO neutrino emissions from the sun, physicists have the so-called 'Borexino detector', pictured - a 55-foot-high, layered, bulb-like machine that contains in its heart a spherical tank called a 'scintillator' Which is filled with 278 tons of a special liquid.

To detect the CNO neutrino emissions from the sun, physicists have the so-called ‘Borexino detector’, pictured – a 55-foot-high, layered, bulb-like machine that contains in its heart a spherical tank called a ‘scintillator’ Which is filled with 278 tons of a special liquid.

When neutrinos from the sun (right) pass through the liquid in the heart of the detector (left), they can interact with its electrons - releasing tiny flashes, whose brightness is indicative of the energy of the neutrino, with those produced by the CNO cycles the deeper end.  These are picked up by camera-like sensors and analyzed by powerful hardware

When neutrinos from the sun (right) pass through the liquid in the heart of the detector (left), they can interact with its electrons – releasing tiny flashes, whose brightness is indicative of the energy of the neutrino, with those produced by the CNO cycles the deeper end. These are picked up by camera-like sensors and analyzed by powerful hardware

Despite the exceptional successes previously achieved and an ultra-clean detector, we have to work hard to improve the suppression and understanding of their low residual backgrounds, ”Dr. Ranucci added.

This, he added, allowed them to “identify the neutrinos of the CNO cycle.”

These findings finally confirm that some of the sun’s energy is actually found through CNO cycle reactions – an idea that was first proposed in 1938.

Borexino experiment spokesperson Marco Pallavisini, who is a physicist at Genoa University, said it was the crowning of a relentless, long-term effort that led us to push the technology.

This, he added, has made ‘the heart of Borexino the smallest radioactive place in the world.’

The full findings of the study are published in the journal Nature.

To ensure that the detector receives only the rare neutrino signals - and is not absorbed by cosmic radiation - the Berexina experiment is buried underground and further discharged by cocooned into a water tank.

To ensure that the detector receives only the rare neutrino signals – and is not absorbed by cosmic radiation – the Berexina experiment is buried underground and further discharged by cocooned into a water tank.


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