Decades of stellar abundance crisis is a fundamental theory of stellar evolution that continuously relies on the internal structure of the Sun, as determined by stellar oscillations (sun-seismic science), and current measurements of solar chemical composition. It is a conflict with the structure derived from. New calculations in solar atmospheric physics provide updated results on the abundance of various chemical constituents that resolve collisions. Surprisingly, the Sun contains more gases, elements and inert gases than previously thought. The strategy used also promises a significantly additional correct estimate of the chemical composition of a common star.
Astrochemistry using spectra
The proven method we are talking about here is spectral analysis. To see the chemical components of the Sun and other stars there, astronomers generally convey the spectrum: a just like rainbow decomposition of sunlight into different wavelengths. William Wollaston 1st observed the stellar spectrum in 1802, rediscovered in 1814 by Joseph von Fraunhofer, and within 10 years, clearly known by physicists Robert Bunsen and Gustav as a sign of the presence of a particular chemical moiety.
A pioneering study by Indian uranologist Meghnad Saha in 1920 linked the strength of these “absorption lines” to the temperature and chemical composition of the star, providing ideas for a physical model of the star. Cecilia Payne-Gaposhkin’s discovery that our sun-like stars are composed primarily of chemical elements and have no trace of heavy chemical composition is based on his research.
Oscillations in the sun that reveal a different story
It was even more startling when the various pieces of the puzzle did not appear to fit into the new observational data that revealed information about our Sun’s inner workings. Since then, astrophysics has relied heavily on the underlying calculations that link spectrum features to star plasma chemical composition and physics. They represent the foundation of millennia of development in our understanding of the physical structure and evolution of stars and exoplanets and the chemical evolution of the cosmos.
A set of well-known (solar physics) observations of the chemical composition of the solar atmosphere reported in 2009 were used to calibrate the most recent standard model of solar evolution. However, in many critical details, the Standard Model’s reconstruction of our favorite star’s interior structure contradicts another set of measurements: helioseismic data or minuscule vibrations throughout the Sun. Very closely followed
Measurements–how the Sun rhythmically expands and contracts in characteristic patterns on timescales ranging from seconds to hours.
The solar abundances crisis
High-precision helios measurements provided results on the internal structure of the Sun, which is inconsistent with standard solar models. According to helioseismology, the so-called convective region of the Sun was significantly larger than predicted by the Standard Model, as the material moves up and down like boiling water. The velocity of the sound waves near the bottom of this region and the total amount of helium in the Sun is different from the standard model predictions. In addition, certain solar neutrino measurements (elusive elementary particles that are difficult to detect and reach directly from the core region of the Sun) are also slightly lower than experimental data.
Beyond local thermal equilibrium calculations
Maria Bergemann, Ekaterina Magg, and colleagues produced a new study that successfully resolved the problem by updating a model based on spectral assessment of the Sun’s chemical composition. Local thermal equilibrium was used in early studies of how a star’s spectrum was created. They reasoned that the energy in each part of the star’s atmosphere would diffuse locally and achieve a state of equilibrium over time. This allows each of these areas to be assigned a temperature, substantially simplifying the calculation.
But by the 1950s, astronomers realized that the painting was oversimplified. Since then, more and more studies have included so-called NonLTE calculations. This means that the assumption of local equilibrium is removed. A full description of how energy is exchanged throughout the system is included in nonLTE calculations. Photons excite or clash with atoms, causing them to be emitted, absorbed, or dispersed. Attention to this detail is rewarded in a stellar atmosphere where the density is too low for the system to reach thermal equilibrium. There, non-LTE computations give significantly different results than their local equilibrium counterparts.
Non-LTE in the Photosphere of the Sun
Maria Bergemann’s group at the Max Planck Institute for Astronomy is a world leader in applying NonLTE calculations to the stellar atmosphere. As part of her Ph.D. in this team, Ekaterina Magg set out to accurately calculate the interaction of radioactive materials in the photosphere. The photosphere is the outside layer from which most of the sunlight comes, from which absorption lines are also imprinted on the solar spectrum.
This study tracks all chemical elements associated with the current model of how stars evolve and applies several independent methods to the Sun’s atoms and their radiation fields. They used previous simulations that take into consideration both plasma velocity and radiative physics to depict the convective area of our Sun (“STAGGER” and “CO5BOLD”). Described the interaction between and ensured consistent results. For comparison with spectral measurements, they selected the highest quality dataset available. The solar spectrum is published by the Institute of Astrophysics and Geophysics at the University of Göttingen. “We are also making great efforts to analyze the statistical and systematic effects that may limit the accuracy of the results,” says Magg.
There will be no inexplicable contradiction between the results of these models and the Helioseismic readings when these new numbers are utilized as inputs to conventional models of solar structure and evolution. A detailed examination of how Magg, Bergemann, and colleagues generate spectral lines is based on a far more complete model of the underlying physics. It has the potential to resolve the Sun’s abundance dilemma.
The new model can easily be applied to stars other than the Sun as an additional bonus. With large-scale studies such as SDSSV and 4MOST yielding high-quality spectra of ever-increasing stars, this advancement has broad implications for the reconstruction of chemical evolution for future analysis of stellar chemistry. Definitely worth it. With more solid feet in our universe than ever before.