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Spectra of different kinds of celestial objectsSpectra of different kinds of celestial objects

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Makemake

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10/17/11 10/17/11 SpectroscopySpectroscopy

Stellar Classification UsingStellar Classification UsingStrength of Absorption LinesStrength of Absorption Lines

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Spectra in sections looked different because emission tubes Spectra in sections looked different because emission tubes contained different elements. Stars have them all.contained different elements. Stars have them all.

BUT, in general, stars to within a fraction of a percentage, all have similar abundances of the elements!

AA bubu ndnd aa nn cc ee ss ii nn thth ee SS unun Element Abundance (% of total) number of atoms Hydrogen 91.2 (71% by mass) Helium 8.7 (27% by mass) Oxygen 0.078 Carbon 0.043 Iron 0.030 Sulfur 0.015 Nitrogen 0.0088 Silicon 0.0045 Magnesium 0.0038 Neon 0.0035

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Classification overview: TextbookClassification overview: Textbook

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Understanding atomsUnderstanding atoms

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He Na

Ca

Fe

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Understanding the guidesUnderstanding the guides

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Qualitative determination of line strengthQualitative determination of line strength

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Identifying 3 lines + assigning element and line strengthIdentifying 3 lines + assigning element and line strength

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41 Cygni data in ExcelGoogle Spreadsheet (see instruction on a handout)

389.1 H8

430.3 “G” band540.7 He II

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Calculating a line strengthCalculating a line strength

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Line strength =1−flux line bottom

flux continuum

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Measuring the strength of 3 linesMeasuring the strength of 3 lines

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1 − 0.450.73 = 0.38

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1 − 0.670.84 = 0.20

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Determining Spectral Type and Surface TemperatureDetermining Spectral Type and Surface Temperature

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0.38

0.20F7 6300