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How Do We Find Planets Around Other Stars?

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    Astronomical Society of the Pacific

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How Do We Find Planets Around Other Stars?

This fun and simple hands-on astronomy activity describes techniques scientists use to find planets orbiting other stars. Learners will spin “stars” to simulate star wobble (astrometry and radial velocity) and will explore the transit method and direct imaging of planets. The pdf contains step-by-step instructions, photos, presentation tips, and links to background information.

Quick Guide

Preparation Time:
Under 5 minutes

Learning Time:
10 to 30 minutes

Estimated Materials Cost:
$5 - $10 per group of students

Age Range:
Ages 6 - adult

Resource Types:
Activity, Simulation


Materials List (per group of students)

  • 3 Foam balls (“stars”): one will have a planet, one will be without a planet
  • 1 Large “Planet” (small ball) attached to a golf tee
  • Alternate Material for large planet on the golf tee: Clay
  • 1 Toothpick
  • Tiny ball of clay (1 mm)
  • A book approximately one inch thick


  • Earth and Space Science
    • Astronomy
      • Stars and Galaxies
      • Light and Optics
  • Physical Sciences
    • Light and Optics
      • Sunlight and Color
    • Vibration and Waves
      • The Doppler Effect
      • Light and Optics
      • Diffraction and Interference


To use this activity, learners need to:

  • see
  • be mobile
  • touch


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Access Rights:

  • Free access



  • All Rights Reserved, Astronomical Society of the Pacific,


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