Outline of concepts to be presented

Expanded description:  This program investigates how we search for "extra-solar planets" or "exoplanets" -- planets that orbit around other stars. This includes an overview of our solar system, some properties of light, an introduction to Kepler's laws of planetary motion, and how astronomers detect planets orbiting around other stars. The two methods of detecting exoplanets covered in this program include the spectroscopic method and the transit method. The program also includes an introduction to how the Kepler mission is searching for exoplanets.


  • Define "stars" and "planets"
  • Overview of the solar system
  • Challenges to finding planets orbiting around other stars; define "exoplanet"
  • Spectroscopic method for detecting planets
  • Show stars in the current sky that are known to have planets
  • Define "habitable zone"
  • Introduction to Kepler's laws of planetary motion
  • Transit method of detecting planets
  • Use sample photometry data to determine a transiting planet's size, orbital period, and distance from it's star
  • Explore some of the planets that the Kepler mission has found

General Concepts

  • Our star, the Sun, is not the only star to have planets orbiting around it -- hundreds of planets have already been detected.
  • The "habitable zone" is the distance from a star that a planet could have liquid water on its surface, and hence support Earth-like life. 
  • Astronomers are currently using two main methods for detecting exoplanets: spectroscopic, and transit.
  • The spectroscopic method uses the light from the star to detect a star's wobble caused by the exoplanet's mass and gravity.
  • The transit method uses variations in a star's brightness to detect events where a planet is passing in front of a star.
  • Kepler's laws of planetary motion can be used to calculate a planet's distance from its star if we know the orbital period.
  • The Kepler Mission uses a spacecraft to measure the brightness of over 100,000 stars in order to detect planets using the transit method.


Connecting to the Classroom

The Strange Planets Lab works well to support and extend a planetary science unit, or a unit on the electromagnetic spectrum. The program could be utilized at the beginning or end of your unit. No assumptions are made about prior knowledge of any of the concepts covered, however, a great deal of content and concepts are covered in the program. We recommend that you follow-up in the classroom after the program to support the concept development.

Pre-Visit Activities you might consider doing in the classroom :

  • Present the following questions for discussion:  What is the difference between a planet and a star? Are there planets orbiting around other stars? Do you think it is possible for life to exist on other planets in our solar system or in other planetary systems?
  • Review the overall structure of the solar system
  • Review basic characteristics of the planets in our solar system

Post-Visit Activities you might consider doing in the classroom :

  • Strange Planets Hand-out:  the planetarian will provide a master copy of a hand-out in which the students will utilize their knowledge of the transit method and photometry to analyze data and determine a planet's size, orbital period, and distance from its star. 
  • Discuss what they learned from the program, and answer questions. Feel free to forward any questions to the planetarian that you can't find answers for.

Vocabulary: some of the words the students will likely encounter

  • exoplanet (or extra-solar planet)
  • habitable
  • spectrum
  • planetary
  • transit (referring to passing in front of)
  • gravity
  • spectroscopy
  • photometry
  • orbit (and orbital period)
  • brightness
  • radius (radii plural)
  • astronomical unit