Development of Stellar Spectroscopy
The father of stellar spectroscopy is Josef von Fraunhofer (1787–1826), the inventor of the German equatorial mount that is so popular with modern amateur astronomers. He was an optician and, in order to measure the dispersive power of lenses, he made his first spectrometer when he was in his mid-twenties. In 1814, he found that there were lines in the spectrum of white light and, out of interest, he turned his instrument to the Sun. Over the next few years, he mapped the positions of 574 dark lines in the solar spectrum,1 and labeled the most prominent of these with letters, beginning the alphabet at the red end of the spectrum. This alphabetic classification survives today when, for example, we refer to the “calcium H line” (3968 Å). He found that Venus’ spectrum has the same dark lines as the solar spectrum, offering further evidence (if it were needed!) that Venus shines with reflected sunlight. Fraunhofer also turned his objective-prism spectroscope to several of the brighter stars and observed clear differences amongst them. Fraunhofer’s other great contribution to modern amateur spectroscopy was his invention of the diffraction grating.
KeywordsRadial Velocity Solar Spectrum Spiral Nebula Dark Line Bright Star
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Bibliography and References
- Hoskin, M (1999) The Cambridge Concise History of Astronomy. Cambridge University Press, ISBN 0521576008.Google Scholar
- Ridpath, I (1997) A Dictionary of Astronomy. Oxford University Press, ISBN 0192115960.Google Scholar
- Sullivan, N (1965) Pioneer Astronomers. Scholastic Book Services, New York.Google Scholar