New calculations resolve a decade-long controversy over the Sun’s chemical composition
The study resolves the apparent contradiction between the methods used so far to determine the Sun's chemical composition and a more innovative and accurate technique for mapping the internal structure of our star
The research, led by the Max Planck Institute for Astronomy (MPIA), involves the participation of IEEC researcher at the Institute of Space Sciences (ICE-CSIC) Aldo Serenelli
A team of scientists, led by the Max Planck Institute for Astronomy (MPIA) in Heidelberg, Germany, has solved the ‘solar abundance crisis’ by revising the models on which the Sun's chemical composition estimates are based. The research, published last Friday, 20 May, in the journal Astronomy & Astrophysics, presents updated results on the amount of chemical elements that our star contains: the Sun consists of more oxygen, silicon, and neon than previously thought.
The proven method used so far to determine the chemical composition of the Sun—or any other star— is spectral analysis, i.e. the decomposition of light into different wavelengths. The depth of the lines in a star's spectrum is related to its temperature and chemical composition. The claim that stars like our own are composed mainly of hydrogen and helium, plus small amounts of heavier chemical elements, is based on this principle.
In the study presented here, in which the researcher at the Institute of Space Studies of Catalonia (IEEC — Institut d’Estudis Espacials de Catalunya) at the Institute of Space Sciences (ICE-CSIC) Aldo Serenelli participates, new methods have been used that show that the relationship between the abundance of these relevant chemical elements and the intensity of the corresponding spectral lines is significantly different from what previous authors had claimed. As a result, the chemical abundances derived from the observed solar spectra are somewhat different from those established in previous analyses.
“We found that, according to our analysis, the Sun contains 26% more elements heavier than helium (metals) than had been deduced in previous studies,” explains Ekaterina Magg, first author of the paper and a PhD student at the MPIA. “The oxygen abundance value turned out to be almost 15% higher than in previous studies,” says Magg. The new values, however, agree well with the chemical composition of primitive meteorites (CI chondrites), which are believed to represent the chemical composition of the early Solar System.
The ‘solar abundance crisis’
The technique of spectral analysis has been at the heart of advances in understanding the chemical evolution of the Universe, as well as the physical structure and evolution of stars and exoplanets over a century. The current standard model of the Sun's evolution is calibrated using a set of measurements of the chemical composition of the solar atmosphere published in 2009. However, a reconstruction of the Sun's internal structure based on this standard model contradicts another set of measurements obtained from high-precision helioseismic data. This discrepancy led to the so-called ‘solar abundance crisis’.
Now, using the solar abundance values from the recently published research, the discrepancy between the results of these models and the helioseismic measurements disappears.
IEEC researcher at ICE-CSIC Aldo Serenelli comments: “The results of this work reposition the Sun as a fundamental reference in stellar physics studies. This is of central importance for several areas of astrophysics and, in particular, for the detailed characterisation of the internal structure of other stars, a fundamental objective of the European Space Agency (ESA) PLATO mission.”
The new methods employed promise considerably more accurate estimates of the chemical compositions of stars in general. At a time when large-scale studies, both present and in progress, are providing high-quality spectra for an increasing number of stars, this advance puts future analyses of stellar chemistry on a firmer footing than ever before, with corresponding implications for the reconstruction of the chemical evolution of our Cosmos.
Press release prepared in collaboration with the Max Planck Institute for Astronomy (MPIA) and the Communication Office of the Institute of Space Sciences (ICE-CSIC).
Main Image
Solar spectrum
Caption: Spectrum of the Sun, obtained with the high-resolution spectrograph NARVAL installed on the Bernard Lyot Telescope at the Observatoire Midi-Pyrénées. The properties of the absorption lines (dark lines) present in spectra like this one allow astronomers to deduce the temperature and chemical composition of a star.
Credit: M. Bergemann / MPIA / NARVAL@TBL.
Links
More information
This research is presented in a paper entitled “Observational constraints on the origin of the elements. IV: The standard composition of the Sun”, by E. Magg et al., that appears published in the journal Astronomy & Astrophysics on 20 May 2022. The paper is available here.
The Institute of Space Studies of Catalonia (IEEC — Institut d’Estudis Espacials de Catalunya) promotes and coordinates space research and technology development in Catalonia for the benefit of society. IEEC fosters collaborations both locally and worldwide and is an efficient agent of knowledge, innovation and technology transfer. As a result of 25 years of high-quality research, done in collaboration with major international organisations, IEEC ranks among the best international research centers, focusing on areas such as: astrophysics, cosmology, planetary science, and Earth Observation. IEEC’s engineering division develops instrumentation for ground- and space-based projects, and has extensive experience in working with private or public organisations from the aerospace and other innovation sectors.
IEEC is a private non-profit foundation, governed by a Board of Trustees composed of Generalitat de Catalunya and four other institutions that each have a research unit, which together constitute the core of IEEC R&D activity: the Universitat de Barcelona (UB) with the research unit ICCUB — Institute of Cosmos Sciences; the Universitat Autònoma de Barcelona (UAB) with the research unit CERES — Center of Space Studies and Research; the Universitat Politècnica de Catalunya · BarcelonaTech (UPC) with the research unit CTE — Research Group in Space Sciences and Technologies; the Spanish Research Council (CSIC) with the research unit ICE — Institute of Space Sciences. IEEC is a CERCA (Centres de Recerca de Catalunya) center.
Contacts
IEEC Communication Office
Barcelona, Spain
Ana Montaner and Rosa Rodríguez
E-mail: comunicacio@ieec.cat
Lead Researcher at IEEC
Barcelona, Spain
Aldo Serenelli
Institute of Space Studies of Catalonia (IEEC)
Institute of Space Sciences (ICE-CSIC)
E-mail: aldos@ieec.cat, aldos@ice.csic.es