An SwRI-led team proposes new solar elemental abundances that potentially reconcile longstanding questions for the first time. A broad set of interdisciplinary data indicates higher levels of carbon, nitrogen and oxygen in the Sun than previously thought, yielding a major advancement in addressing the prolonged solar abundances problem between spectroscopy and helioseismology measurements. Credit:NASA/ SDO/ AIA.
Solar and cosmochemical data indicate high levels of carbon, nitrogen and oxygen in the Sun, according to research from SwRI.
A Southwest Research Institute-led team combined compositional data of primitive bodies like Kuiper Belt objects, asteroids and comets with new solar data sets to develop a revised solar composition that potentially reconciles spectroscopy and helioseismology measurements for the first time.
Helioseismology probes the Sun’s interior by analysing the waves that travel through it, while spectroscopy reveals the surface composition based on the spectral signature produced by each chemical element.
Dr Ngoc Truong, an SwRI postdoctoral researcher, said: “This is the first time this kind of interdisciplinary analysis has been done, and our broad data set suggests more abundant levels of solar carbon, nitrogen and oxygen than previously thought.
“Solar system formation models using the new solar composition successfully reproduce the compositions of large Kuiper Belt objects (KBOs) and carbonaceous chondrite meteorites, in light of the newly returned Ryugu and Bennu asteroid samples from JAXA’s Hayabusa-2 and NASA’s OSIRIS-REx missions.”
New measurements
To make this discovery, the team combined new measurements of solar neutrinos and data about the solar wind composition from NASA’s Genesis mission, together with the abundance of water found in primitive meteorites that originated in the outer solar system.
They also used the densities of large KBOs such as Pluto and its moon Charon, as determined by NASA’s New Horizons mission.
Truong said: “This work provides testable predictions for future helioseismology, solar neutrino and cosmochemical measurements, including future comet sample return missions.
“The solar composition is used to calibrate other stars and understand the composition and formation of solar system objects.
“These breakthroughs will enhance our understanding of the primordial solar nebula’s chemistry and the formation of numerous solar system bodies.”
New understanding
The team examined the role of refractory, tar-like organic compounds as a major carrier of carbon in the protosolar nebula.
Solar system formation models using measurements of organics from comet 67P/ Churyumov-Gerasimenko and the most widely adopted solar composition ratios did not produce the dense, rocky Pluto – Charon system.
SwRI’s Dr Christopher Glein, an expert in planetary geochemistry, added: “With this research, we think we finally understand the mix of chemical elements that made the solar system.
“It has more carbon, nitrogen and oxygen than what is currently assumed.
“This new knowledge gives us a firmer basis for understanding what element abundances in giant planet atmospheres can tell us about the formation of planets. We already have our eyes on Uranus — NASA’s next target destination — and beyond.”
In the search for habitable exoplanets, scientists measure the abundances of elements in stars spectroscopically to infer what a star’s orbiting planets are made of, using stellar composition as a proxy for its planets.
Truong said: “Our findings will significantly affect our understanding about the formation and evolution of other stars and planetary systems, and even further, they enable a broader perspective of galactic chemical evolution.”
The paper is published in the AAS Astrophysical Journal.
