Researchers detect CNO neutrinos in the sun's core

Researchers from Princeton have announced that they have been able to detect CNO neutrinos, tiny particles pointing to the presence of carbon, nitrogen, and oxygen inside the core of the sun. The particles are said to reveal the last missing detail of the fusion cycle that powers the sun and other stars. These are a rare type of neutrinos known as "ghost particles" because they're able to pass through most matter without leaving a trace.

The discovery was made using the Borexino detector, which is an enormous underground experiment located in central Italy. The project is a multinational one supported by the United States and other countries. Detection of the ghost particle confirms predictions from the 1930s that some of the sun's energy is generated by a chain of reactions involving carbon, nitrogen, and oxygen (CNO).

The reaction produces less than one percent of the sun's energy but is believed to be the primary energy source in larger stars. This process produces two neutrinos, which are the lightest known elementary particles of matter, along with other subatomic particles and energy. Neutrinos are also released by the hydrogen-to-helium fusion process in more abundance.

Researchers note the spectral signatures of the two types of neutrinos are different, and scientists can identify each of them. Scientists say that in stars like the sun, fusing hydrogen into helium predominantly happens through proton-proton chains. In heavier and hotter stars, carbon and nitrogen catalyze hydrogen to burn and release CNO neutrinos.

The discovery of the neutrinos confirms CNO is at work within the sun and can help resolve an open question in stellar physics of how much the sun's interior is made up of metals. Researchers point out that neutrinos are exceedingly difficult to measure, with more than 400 billion of them hitting every square inch of the surface of the earth every second. Virtually all of those particles pass through the entire planet without interacting with anything. Measuring them requires a very large and carefully protected instruments such as Borexino.