Desktop Stars


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The purpose of this lesson is to gain an understanding of the techniques astronomers use to measures the distance to and speed of distant stars and galaxies.


Students will explore the techniques astronomers use to measure the distance to, composition of, and speed of distant stars and galaxies through a series of hands-on activities using desktop light sources. Students learn how to take and graph scientific data, and to interpret the results. Students have the option of choosing from several differnet Internet research project designed to allow further exploration of the ideas contained in the hands-on activities.


  1. Inverse Square Law (Part 1)
    • Students will measure the variation of the brightness of a light with distance and compare their results to the inverse square law.
    • Students will discuss the use of the inverse square law to measure distance to a light.
  2. Light and Spectra (Part 2)
    • By using a diffraction grating or spectrometer, students will observe that light can be split into different wavelengths, which correspond to different colors.
    • Students will measure the wavelengths at which each of several elements emit light.
    • Students will demonstrate an understanding of the methods astronomers use to measure the composition of distant stars and galaxies by identifying some of the gases present in a fluorescent light bulb.
  3. The Expanding Universe (Part 3)
    • Students will explore the Doppler effect, which describes the change in wavelength of the light emitted from a moving source.
    • Students will understand that the Doppler effect can be used to measure the speed of distant galaxies, and that the primary evidence that the universe is expanding is that these galaxies are moving away from the earth.
    • Students will estimate the age of the universe by combining a distance measurement using the inverse square law with a measurement of the speed of the galaxy obtained using the Doppler effect.