The solar abundance problem: determining accurate helium abundance and age of the Sun
Supervisor: Günter Houdek
Contact information: guenter.houdek@univie.ac.at
Expected duration: 9 months
Project description & Goals:
The helium abundance and age of the Sun are important reference values for the theory of stellar structure and evolution and consequently also for other fields in astrophysics such as galactic archeology. The solar abundance problem refers to the discrepancy between our best solar model computations, so-called standard solar models, and accurate measurements of the solar interior obtained from helioseismic observations. Helioseismology is the method with which the interior solar structure can be determined from analysing thousands of measured frequencies of acoustic oscillations in the Sun, similar to the tones of a musical instrument. These oscillation frequencies are measured with a higher accuracy than we know the gravitational constant. The aim of this project is to determine accurate values of the solar helium abundance and age using updated opacity tables reflecting the latest determination of the solar chemical composition (Magg et al. 2022). The method to be used is that of Houdek & Gough (2011), who used a new seismic diagnostic technique for determining an accurate solar age and a proxy for the solar helium abundance. This involved evolutionary computations and frequency calculations, which will be performed with the provided programmes ASTEC and ADIPLS (Christensen-Dalsgaard 2008). The model results will be compared to frequency data obtained from the BiSON (Birmingham Solar Oscillations Network). The outcome of this project will be a new standard solar model providing new and more accurate values for the solar age and heavy-element abundance, and which is in good agreement with helioseismic measurements.
Working plan & Milestones (including final thesis):
- Literature study and introduction to stellar evolution and oscillations.
- Familiarization with the provided programmes ASTEC and ADIPLS, as well as with the seismic diagnostic of Houdek & Gough (2007).
- Reproduce results of Houdek & Gough (2011) for learning and testing purposes.
- First computations with the new, provided, opacity tables to produce preliminary results.
- Calibrate a new standard solar model.
- Start writing thesis chapters.
- Final results. Completed thesis.
Requirements / special skills:
Basic knowledge of stellar physics and data handling (e.g. plotting of results).
References:
Christensen-Dalsgaard J. 2008, Ap & SS.316, 13, https://link.springer.com/article/10.1007/s10509-007-9675-5
Christensen-Dalsgaard J. 2008, Lecture Notes, http://astro.phys.au.dk/~jcd/evolnotes/LN_stellar_structure.pdf
Houdek G. & Gough D. 2007, Mon. Not. R. Astron. Soc. 375, 861, http://dx.doi.org/10.1111/j.1365-2966.2006.11325.x
Houdek G. & Gough D. 2011, Mon. Not. R. Astron. Soc. 418, 1217, http://dx.doi.org/10.1111/j.1365-2966.2011.19572.x
Magg E. et al. 2022,https://arxiv.org/pdf/2203.02255.pdf