After many years of debate, scientists have become toward identifying precisely what the sun — and as a result, the entire universe — is made of.
The sun is frequently composed of hydrogen and helium. There also are heavier factors consisting of oxygen and carbon, however simply how tons is controversial.
New observations of ghostly subatomic debris called neutrinos advocate that the sun has a sufficient delivery of “metals,” the time period astronomers use for all factors heavier than hydrogen and helium, researchers document May 31 at arXiv.org.
According to Livia Ludhova, a physicist at Germany's Research Center Jülich, the results "are absolutely well-matched with [a] excessive metallicity" for the sun.
Elements heavier than hydrogen and helium are critical for growing rock-iron planets like Earth and maintaining lifestyles-paperwork like humans. By some distance, the maximum ample of those factors withinside the universe is oxygen, observed via way of means of carbon, neon, and nitrogen.
But astronomers don’t realize precisely how tons of those factors exist relative to hydrogen, the maximum not unusual place detail withinside the cosmos. That’s due to the fact astronomers normally use the sun as a reference factor to gauge elemental abundances in different stars and galaxies, and strategies mean very distinctive chemical compositions for our star.
One approach exploits vibrations in the interior of the sun to infer its inner shape and favors an excessive steel content. The 2d approach determines the sun’s composition from how atoms on its floor take in sure wavelengths of light.
Two many years ago, the use of this 2d approach cautioned that oxygen, carbon, neon, and nitrogen tiers withinside the sun had been 26 to forty-two percent decrease than an in advance dedication found, growing the cutting-edge conflict.
Another approach has now emerged that might determine the lengthy-status debate: the use of solar neutrinos.
This debris rises up from nuclear reactions withinside the sun’s center that flip hydrogen into helium. About 1 percentage of the sun’s electricity comes from reactions involving carbon, nitrogen, and oxygen, which convert hydrogen into helium however now no longer get used up withinside the process.
So the greater carbon, nitrogen, and oxygen the sun clearly has, the greater neutrinos this CNO cycle must emit.
In 2020, scientists introduced that Borexino, an underground detector in Italy, had noticed those CNO neutrinos (SN: 6/24/20).
Now Ludhova and her colleagues have recorded sufficient neutrinos to calculate that carbon and nitrogen atoms collectively are approximately 0.06 percent as ample as hydrogen atoms withinside the sun — the primary use of neutrinos to decide the sun’s makeup.
And even though that range sounds small, it’s even better than the only desired via way of means of astronomers who aid an excessive-steel sun. And it’s 70 percent extra than the range a low-steel sun must-have.
“This is an exceptional result,” says Marc Pinsonneault, an astronomer at Ohio State University in Columbus who has lengthy encouraged for an excessive-steel sun. “They’ve been capable of revealing robustly that the cutting-edge low-metallicity answer is inconsistent with the data.”
Still, due to uncertainties in each of the located and expected neutrino numbers, Borexino can’t absolutely rule out a low-steel sun, Ludhova says.
The new paintings are “a giant improvement,” says Gaël Buldgen, an astrophysicist at Geneva University in Switzerland who favors a low-steel sun. But the expected numbers of CNO neutrinos come from fashions of the sun that he criticizes as too simplified.
Those fashions forget the sun’s spin, which could result in the blending of chemical factors over its lifestyles and extrude the quantity of carbon, nitrogen, and oxygen close to the sun’s center, thereby converting the expected range of CNO neutrinos, Bulgin says.
Additional neutrino observations are wished for a very last verdict, Ludhova says. Borexino closes down in 2021, however destiny experiments should fill the void.
The stakes are excessive. “We’re arguing approximately what the universe is made of,” Pinsonneault says, because “the sun is the benchmark for all of our studies.”
So if the sun has tons greater carbon, nitrogen, and oxygen than presently thought, so does the entire universe. “That adjustments our information approximately how the chemical factors are made.
It adjustments our information of the way stars evolve and the way they stay and die,” Pinsonneault says. And, he adds, it’s a reminder that even the best-studied star — our sun — has secrets.
Borexino collaboration. Improved measurement of solar neutrinos from the carbon-nitrogen-oxygen cycle by Borexino and its implications for the standard solar model. arXiv:2205.15975. Submitted May 31, 2022.
M. Asplund et al. The chemical composition of the sun. Annual Review of Astronomy and Astrophysics. Vol. 47, 2009, p. 481. doi: 10.1146/annurev.astro.46.060407.145222.
E. Anders and N. Grevesse. Abundances of the elements: meteoritic and solar. Geochimica et Cosmochimica Acta. Vol. 53, January 1989, p. 197. doi: 10.1016/0016-7037(89)90286-X.