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THE IB SAYS
THE IB SAYS
Understandings: Stellar spectra
Applications and skills: Explaining how the chemical composition of a star may be determined from the star’s spectrum
Data booklet reference: λ T = 2.9×10−3 m K
My vodcast
My vodcast
Fraunhofer lines
Fraunhofer lines
In 1814 Joseph von Fraunhofer studied, in detail, the spectrum of the sun and described over 500 dark lines in its spectrum. William Hyde Wollaston had described five lines he observed in 1802, but Fraunhofer's description was much more detailed. Neither, however, offered a convincing explanation of what caused the lines. Fraunhofer also observed the lines in the spectrum of Sirius, the brightest star in the sky (after the Sun).
A complete explanation of why the lines appear where they do would need to wait for Niels Bohr and his model of the atom, but Gustav Kirchhoff (a polymath who, amongst other feats, was the inventor of the term black body radiation) and Robert Bunsen both, independently, showed in 1859 that the lines were associated with chemical elements.
Exploring stellar spectra using the SDSS
Exploring stellar spectra using the SDSS
The Sloan Digital Sky Survey is an ongoing project to create a database of celestial objects and includes spectral data for many. My video on this page describes how to use it, but the most recent version of the survey is accessible here: https://www.sdss.org/
Resources from textbooks
Resources from textbooks
Oxford Physics: pp 650 - 651, including a worked example on page 652
Hamper HL (2014): p 542
Relevant questions from Dot Point Physics (E. Astrophysics)
Relevant questions from Dot Point Physics (E. Astrophysics)
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