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Elusive “ghost particles” produced deep within the Sun have been detected for the first time, helping to shed light on the reactions that make massive stars glow.
Researchers were able to capture evidence of the particles as they passed through a special detector buried under a mountain near the town of L’Aquila, Italy.
The rare emissions – which have traveled 90 million kilometers to reach us – are produced in certain nuclear reactions that make up less than one percent of solar energy.
However, these reactions are believed to be more dominant in larger stars – and may help explain their formation and evolution.
Elusive “ghost particles” produced deep within the Sun have been detected for the first time, helping to shed light on the reactions that make massive stars glow. Researchers were able to capture evidence of the particles as they passed through a special detector buried under a mountain near the town of L’Aquila, Italy. In the photo, the heart of the Borexino detector
“We finally have the first experimental and groundbreaking confirmation of how stars heavier than the sun shine,” said author and astroparticle physicist Gianpaolo Bellini of the University of Milan.
Stars are powered by the fusion of hydrogen into helium, which can occur through two different processes – the first being the so-called proton-proton chain, which only involves the 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 these three elements help catalyze nuclear reactions – becomes a more important source of energy. It also releases ghostly particles called neutrinos.
These are almost massless – and are able to traverse ordinary matter without giving up any indication of their presence.
However, physicists wanted to study these emissions from the Sun, because a better understanding of how the CNO cycle works in our star will provide a better understanding of how larger stars – where this process is dominant – burn their nuclear fuel.
To detect CNO neutrino emissions from the sun, physicists used the so-called “ Borexino detector ” – a 55-foot-tall, layered onion-shaped machine that contains at its core a spherical reservoir called “ scintillator ” filled with 278 tons of a special liquid.
When neutrinos pass through this liquid, they can interact with its electrons – releasing tiny flashes of luminosity indicative of the neutrino’s energy, those produced by the CNO cycle being at the more intense end.
These are picked up by sensors similar to cameras and analyzed by powerful equipment.
To make sure the detector only picks up rare neutrino signals – and isn’t overwhelmed by cosmic radiation – the Borexino experiment is both buried underground and protected by being cocooned in a reservoir of water.
“It is the culmination of a thirty-year effort that began in 1990 – and 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 must be attributed to the “unprecedented purity” of the solution.
Detection of CNO neutrinos revealed how much the sun is made up of the elements carbon, nitrogen and oxygen.
To detect CNO neutrino emissions from the sun, physicists used the so-called “ Borexino detector, ” shown – a 55-foot-high layered onion-shaped machine that contains at its core a spherical reservoir called “ scintillator ” which is filled. with 278 tons of a special liquid.
As the Sun’s neutrinos (right) pass through the liquid in the detector’s core (left), they can interact with its electrons – releasing tiny lightning bolts whose brightness is indicative of the neutrino’s energy, those produced by the CNO cycle being turned on. the most intense ending. These are captured by camera type sensors and analyzed by powerful equipment
“Despite the outstanding successes achieved previously and an already ultra-pure detector, we had to work hard to further improve the suppression and understanding of very faint residual backgrounds,” added Dr Ranucci.
This, he continued, enabled them “to identify neutrinos in the CNO cycle”.
The discovery finally confirms that some of the sun’s energy is indeed produced by CNO cycle reactions – a notion that was first proposed in 1938.
“This is the culmination of a relentless, years-long effort that has led us to push the technology beyond any previously reached limits,” said Borexino Experiment spokesperson Marco Pallavicini, University physicist. from Genoa.
This, he added, made the “core of Borexino the least radioactive place in the world”.
The full results of the study were published in the journal Nature.
To make sure the detector only picks up rare neutrino signals – and isn’t overwhelmed by cosmic radiation – the Borexino experiment is both buried underground and protected by being cocooned in a reservoir of water.
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