For the first time, scientists detect the ghostly signal that reveals the engine of the universe

In research published Wednesday in the journal Nature, scientists reported making the first detection of almost ethereal particles called neutrinos that can be traced to the carbon-nitrogen-oxygen fusion, known as the CNO cycle, inside from the sun.

It’s a historic discovery that confirms theoretical predictions from the 1930s, and it’s hailed as one of the greatest physics discoveries of the new millennium.

“This is truly a breakthrough for solar and stellar physics,” said Gioacchino Ranucci of the Italian National Institute of Nuclear Physics (INFN), one of the researchers on the project since its launch in 1990.

Scientists used the highly sensitive Borexino detector at INFN’s Gran Sasso Particle Physics Laboratory in central Italy, the world’s largest underground research center, deep in the Apennines, about 65 miles south northeast of Rome.

The detection ends decades of study of neutrinos from the sun by the Borexino Project and reveals for the first time the primary nuclear reaction most stars use to fuse hydrogen into helium.

Almost all stars, including our sun, give off enormous amounts of energy by fusing hydrogen into helium – an efficient way to “burn” hydrogen, the simplest and most abundant element and the main one. fuel source of the universe.

In the sun’s case, 99% of its energy comes from proton-proton fusion, which can create beryllium, lithium, and boron before breaking them down into helium.

But most of the stars in the universe are much larger than our sun: the red giant Betelgeuse, for example, is about 20 times as massive and about 700 times as wide.

Large stars are also much hotter, which means they are extremely fueled by CNO fusion, which fuses hydrogen into helium by means of atomic nuclei transformed into an endless loop between carbon, nitrogen and l ‘oxygen.

The CNO cycle is the main source of energy in the universe. But it’s hard to spot it inside our relatively cool sun, where it only makes up 1% of its energy.

The giant Borexino detector searches for neutrinos emitted during nuclear fusion in the heart of the sun.

Neutrinos barely interact with anything, so they’re ideal for studying nuclear reactions from a distance – but they’re also extremely difficult to detect.

Billions of neutrinos from the sun pass through the Borexino detector every second, but it only detects dozens of them every day, looking for faint flashes of light as they decay in its dark 300-ton reservoir of water.

Ranucci said the Borexino detector spent decades measuring neutrinos from the sun’s main proton-proton chain reaction, but it was very difficult to detect its CNO neutrinos – only seven neutrinos with the telltale energy of the cycle NOCs are spotted in one day.

The discovery has required making the detector even more sensitive over the past five years, he said, by protecting it from outside sources of radioactivity so that the detector’s inner chamber is the most radiation-free place on the planet. Earth.

The result is the only direct sign of CNO merger ever seen anywhere: “It is the first evidence that the CNO cycle is at work in the sun and the stars,” said Ranucci.

Gabriel Orebi Gann, a particle physicist at the University of California at Berkeley, called the discovery a “major milestone.”

“This discovery brings us closer to understanding the composition of our sun’s core and the formation of heavy stars,” she said.

Orebi Gann is the author of a scientific article in Nature on the new study, but she was not involved in the research.

Neutrinos are produced naturally in nuclear reactions and pass through most matter with no effect, so they can be used to probe otherwise inaccessible regions of the universe, she said.

For this reason, several neutrino detectors monitor their ephemeral presence in the dark around the world, including the IceCube Observatory at the South Pole and the Super-Kamiokande detector in Japan.

It’s theorized that Big Bang neutrinos could account for some of the universe’s mysterious “dark matter” – vast invisible halos around stars and galaxies that make up about a quarter of its mass.

Orebi Gann said that an asymmetry between neutrinos and their antiparticles could also explain the apparent dearth of anti-matter in our universe and its dominance over normal matter – in other words, simply why there is something here. , rather than absolutely nothing.