Mars for Earthlings > Lesson Modules > In-Class Activity 1- Seeing Like Kepler

Seeing Like Kepler

In-Class Activity 1_Seeing Like Kepler

Julia Kahmann-Robinson PhD and Marjorie Chan PhD, University of Utah Department of Geology & Geophysics


Understand explain how Kepler locates planets outside our solar system.


  1. Purchase or make an orrery (model planet system)
  2. Have Internet access in the classroom


  1. Orrery suggestions for building:
  2. Kepler Mission:
  3. Kepler Exoplanet Transit Hunt:


Show students a model planet system (orrery) and ask students how they might be able to detect the planet orbiting its sun if it is thousands of light years away.


Ask students what problems might they encounter in trying to detect a planet orbiting a star.

  • The sun is far brighter than the planet and you just can't see it because planets are not as bright.
  • The planet is too small for detection.

Have students interact with the online Kepler Exoplanet Transit Hunt simulation:

Students will:

  1. Choose and record the star system they are observing
  2. Manually record and make calculations throughout the simulation. Record calculations below:
  3. At the end of the simulation, what kind of planet did the students find? The programs offers an "artist's rendition" of the planet surface....what does it look like?
  4. Determine if their star system has a planet in the habitable zone. Have students explain their reasoning for why or why not the planet is in the habitable zone.


Transit method of detecting planets ( ):

When a planet crosses in front of its star as viewed by an observer, the event is called a transit. Transits by terrestrial planets produce a small change in a star's brightness of about 1/10,000 (100 parts per million, ppm), lasting for 2 to 16 hours. This change must be absolutely periodic if it is caused by a planet. In addition, all transits produced by the same planet must be of the same change in brightness and last the same amount of time, thus providing a highly repeatable signal and robust detection method. Credit: NASA.


Have students brainstorm:

  1. A detection method for determining an exoplanet.
  2. Criteria for the "habitable zone" (size of star, proximity of orbiting planet, size of planet, etc.).


  1. From students experience in the Kepler simulation what is the habitable zone and how does it relate to Earth? What criterion makes a zone "habitable"?
  2. Ask students to explain the "transit method" of detecting planets.