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Survey of the Universe: Stars, Spectra, and Classification

Learn about the classification of stars based on their spectra and surface temperature. Discover the contributions of women astronomers and their significant work in cataloguing stellar spectra. Explore the concept of absorption lines in stellar spectra. Any questions?

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Survey of the Universe: Stars, Spectra, and Classification

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  1. Survey of the UniverseTom Burbinetburbine@mtholyoke.edu

  2. HW • HW #4 and #5 are due this Wednesday

  3. Stars have different colors

  4. Surface Temperature • Determine surface temperature by determining the wavelength where a star emits the maximum amount of radiation • Surface temperature does not vary according to distance so easier to measure

  5. 1913

  6. Who were these people? • These were the women (called computers) who recorded, classified, and catalogued stellar spectra • Were paid 25 cents a day • Willamina Fleming (1857-1911) classified stellar spectra according to the strength of their hydrogen lines • Classified over 10,000 stars

  7. http://www.youtube.com/watch?v=R6_dZhE-4bk

  8. Fleming’s classification • A - strongest hydrogen lines • B - slighter weaker lines • C, D, E, … L, M, N • O - weakest hydrogen lines lines

  9. Annie Jump Cannon (1863-1941) • Cannon reordered the classification sequence by temperature and tossed out most of the classes • She devised OBAFGKM • http://andyrivkin.bandcamp.com/track/obafgkm

  10. More information • Each spectral type had 10 subclasses • e.g., A0, A1, A2, … A9 in the order from the hottest to the coolest • Cannon classified over 400,000 stars

  11. OBAFGKM • Oh Be A Fine Girl/Gal Kiss Me

  12. http://physics.uoregon.edu/~jimbrau/BrauImNew/Chap04/FG04_05.jpghttp://physics.uoregon.edu/~jimbrau/BrauImNew/Chap04/FG04_05.jpg

  13. http://spiff.rit.edu/classes/phys301/lectures/spec_lines/spec_lines.htmlhttp://spiff.rit.edu/classes/phys301/lectures/spec_lines/spec_lines.html

  14. http://scope.pari.edu/images/stellarspectrum.jpg

  15. absorption line - A dark feature in the spectrum of a star, formed by cooler gas in the star's outer layers (the photosphere) that absorbs radiation emitted by hotter gas below.

  16. Any Questions?

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