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Scientists using the Borexino neutrino observatory in Italy say they have detected a previously undetected type of solar neutrino. These newly detected neutrinos – or nearly massless subatomic particles – are produced by the “secondary” part of the Sun’s nuclear fusion cycle. Although the discovery itself is exciting, scientists say the new neutrinos will eventually help illuminate the mysterious core of the Sun. As well as all other stellar cores in the universe.
Bornexio Collaboration
NBC News reported on the discovery, which the team of scientists described in a paper recently published in the journal Nature. In the paper, the team, all from the international Borexino collaboration, claims that solar neutrinos like these are the only “direct probe” into the Sun’s deep interior.
For those unfamiliar with, neutrinos are similar to electrons, except for the crucial difference that they do not carry an electrical charge. Instead, as the name suggests, neutrinos are electrically neutral. This means that subatomic particles do not interact with electromagnetic fields. And because neutrinos have such small mass – they are each 10 billion billion billion times less massive than a grain of sand – they barely interact with matter.
Bornexio Collaboration
This new type of solar neutrino arises due to a particular part of the Sun’s nuclear fusion cycle. As is the case with all stars, the Sun beats together and fuses the elements into its core, subsequently releasing energy. These recently discovered solar neutrinos are released during the part of the fusion cycle that converts hydrogen to helium, known as the carbon-nitrogen-oxygen (or CNO) cycle.
Scientists claim that these particular solar neutrinos will provide information about the Sun’s core, because the level at which they are emitted depends on the elemental composition of the star. This is because the metal content of a star’s core affects the rate at which the CNO cycle produces neutrinos. (In this context, scientists consider anything heavier than helium a metal.)
Kelvinsong
Consequently, depending on the variations in CNO neutrinos detected by scientists on Earth, it is possible to make estimates of the Sun’s core. Or of other stellar nuclei, for that matter. Furthermore, scientists could better collect a star’s temperature and density and the opacity of its outer layers. (All features that might provide a better sense of a star’s evolutionary history.)
As for how the scientists were able to capture these neutrinos, it was a matter of perfectly calibrating the observatory. The underground observatory, in the images above, is part of the largest underground research center in the world and works by detecting the light produced when neutrinos scatter electrons. The electrons themselves are found inside a large scintillator pool; that is, a liquid medium that produces light in response to the passage of charged particles.
Antonio Ciccolella
Moving forward, the Bornexio Collaboration says it wants to improve the accuracy of its neutrino detections. This will largely come from innovative methods of eliminating background radiation, which can interfere with neutrino detection. If they are able to do this, scientists say they will be able to develop a much better understanding of the Sun and how massive stars are formed in general.
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