Describe how spectra can provide information on surface temperature, rotational and translational velocity, density and chemical composition of stars

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Describe how spectra can provide information on surface temperature, rotational and translational velocity, density and chemical composition of stars

  • Surface temperature can be obtained by observing the dominant wavelengths of a star’s spectrum and comparing this to a black body.
  • The type and intensity of absorption spectrum can also indicate surface temperature.
  • Translational velocity can be determined by the Dopper effect, i.e. red and blue shifts.
  • Red shift indicates travelling away, while blue shift indicates travelling towards observer (BTRA – Buy Two Red Apples).
  • Rotational velocity can be determined by both red and blue shifts of the opposite sides of a rotating body, which results in the broadening of spectral lines.
  • Density can be inferred from pressure.
  • Pressure is determined by examining width of spectral lines.
    • Low pressures – sharp.
    • High pressures – broad.
  • Chemical composition can be determined by comparing absorption spectrum with known absorption and emission spectrum of elements, ions, and molecules on Earth.