The sun contains more oxygen and metals. A new study has solved a ten-year dilemma about the chemical composition of the star

For almost 10 years, scientists have been unable to determine the internal structure of the Sun because the results they obtained using two different research methods contradicting each other. However, new calculations by solar physicists are updating data on the content of various chemicals and resolving this conflict.

The first method relied on spectral analysis – the decomposition of light into waves of different lengths. Stellar spectra contain noticeable dark lines indicating the presence of certain chemical elements. As early as 1920, these lines were associated with the temperature of the star and its chemical composition. This is how scientists have suggested that the Sun and other similar stars consist mainly of hydrogen and helium. This standard model was later calibrated using solar atmospheric measurements published in 2009.

However, the model obtained in this way contradicts the one based on another method of research – helioseismology. It accurately tracks how the Sun is rhythmically compressed and expanded in a characteristic rhythm in time intervals from seconds to hours. Just as seismic waves can tell geologists about the structure of the Earth, helioseismic waves provide data about the structure of the Sun.

According to the helioseismic model, the convection zone inside the Sun, where matter actively mixes and transfers energy from the inner to the outer layers, is much larger than the standard model predicted. Other measurements, such as the total amount of helium in the Sun, also did not match.

Spectrum of the Sun taken with a NARVAL high resolution spectrograph. The image shows dark lines that allow astronomers to determine the temperature and chemical composition of the star. Credit: M. Bergemann/MPIA/NARVAL@TBL

For almost 10 years, astronomers could not solve this dilemma until researchers Katerina Magg, Maria Bergemann and their colleagues revised the model on which the spectral analysis of the Sun was based. They tracked all the chemical elements that correspond to modern models of stellar evolution. Scientists have also described the interaction between the Sun’s atoms and its radiation field using several independent methods.

This helped them find that the Sun contains 26% more elements heavier than Helium, which in astronomy are called metals. They also determined that the Sun has 15% more oxygen than previously thought.

When this new data is used to build models of solar structure and evolution, the discrepancy disappears. The new models are more realistic. They give the most accurate idea of ​​the composition of the Sun. They can also be applied to other similar stars, which greatly expands the arsenal of astronomers.