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Spectra

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Spectra

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  1. Spectra

  2. Three Types of Spectra

  3. Made by a hot solid object or a high pressure gas Hotter: Shorter Peak Wavelength Continuous Spectra

  4. Continuous Spectra • Made by a hot solid object or a high pressure gas • Hotter: • More intense (more energy released per area) • Stefan-Boltzmann Law • Intensity is proportional to Temperature4 • 2 times hotter = 16 times as intense • 3 times hotter = 81 times as intense • 4 times hotter = 256 times as intense

  5. H & Ne

  6. Bright-Line SpectraEmission Spectra

  7. Emission lines (top) and absorption lines (bottom) of Hydrogen.

  8. Absorption Lines from the Atmosphere of the Sun

  9. Absorption Lines

  10. Ionization • As the temperature increases fewer molecules and fewer atoms are stable and can therefore cause absorption lines • If you know the lines, you know the temperature.

  11. Doppler Effect

  12. Doppler Effect

  13. What is the radial velocity of Barnard's star? • 612.00nm • 610.05nm

  14. 612.00nm 612.25 – 612.00 = 0.25 .25 / 612.25 = .000408 .000408 × 2.99 × 105 = 122 km /sec 610.00nm 610.30 – 610.05 = 0.25 .25 / 610.00 = .000409 .000409 × 2.99 × 105 = 122 km /sec

  15. Barnard’s Star • Visual Magnitude 9.54 • Absolute Magnitude13.24 • Spectral Type M 3.8 • Distance 5.96 light-years • Luminosity 0.0004 Lsun • Mass 0.17 Msun • Temperature 3,134 K • Position R.A. 17h 57 m 48.5s Dec. +04° 41' 36"

  16. Motion over a two month period.

  17. Largest Proper Motion • 10.3 arc-sec / year • 5.96 ly

  18. How fast is it moving? • 5.96 ly × 9.5 × 1012 km / ly = 5.66 × 1013 km • 10.3 arc-sec/ yr = .00286 degrees / yr • Tan.00286 × (5.66 × 1013 km) = = 2.83 × 109 km / yr = 90 km/ sec