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NAAP Hertzsprung-Russell Diagram — Pedagogical Objectives

Spectral Type

  • Student will understand the differences between absorption, emission, and continuos spectra.
  • Student will be able to create a geometry consistent with each of the above spectra.
  • Student will be able to recite the spectral type order – OBAFGKM.
  • Student will identify O stars with the hottest stars and M with coldest stars.
  • Student will identify the sun as a G2 star.
  • Student will be able to demonstrate that color is related to temperature.


  • Student will be able to work with the luminosity equation.
  • Student will be able to demonstrate the influence of radius and temperature on luminosity.
  • Student will know the mass-luminosity relationship for main sequence stars.
  • Student will understand that there are different luminosity classes – identifiable by stellar spectra.

HR Diagram

  • Student will understand the HR diagram axes and different ways of expressing those axes.
  • Student will be able to identify the orientation of increasing values of the axes.
  • Given a star, the student will be able to approximate what kind of star it is: supergiant, giant, dwarf, red dwarf, or white dwarf.
  • Student will be aware of observational bias with respect to the nearest stars and brightest stars.
  • Student will be able to orient the isoradius curves and approximate their values.