Investigating Astronomy logo
Home  |  About IA  |  For Families  |  For Teachers
Doing Science

Unit Three: Investigating Planets
Doing Science

2. Extrasolar Planetary Systems

For centuries, the only known planets were those circling our own sun. It was not even known if planets were rare or common in the universe. In the past 20 years, however, hundreds of planets have been discovered around other stars. Several stars are known to have more than one planet. How do these new planetary systems compare with our own? Are the planets near to their parent star or far away? Are they all the same size? Do they all orbit in the same plane like the planets in our system, or are the orbits all askew? In this Doing Science, you will investigate how different (or the same) extrasolar planetary systems from our own.

Go to the Extrasolar Planets Encyclopedia at:, select the Interactive Catalog, and then All Candidates Detected. That will bring up the latest list of known extrasolar planets. The table includes information about the star (click on the planet's name), and estimates of the masses of the planets and parameters describing their orbits—enough information to make your own drawing or model of the system. Select a few representative systems and use the techniques developed in the module to make your own model of each system, either using clay or making a scale drawing. For systems including more than one planet, see if you can think of a way to show how the orbits are oriented to each other. How are these systems different or the same as our solar system?

Your Report:

  1. Prepare a display showing your drawings or physical models. Provide a written description of each and a comparison of the modeled systems with our own. Are there any similarities? How are they different? Can you estimate the surface temperatures of the extrasolar planets?
  2. Participate in the search for an extrasolar planet! If you have access to a good telescope, you can join one of the teams actively searching for more extrasolar planets. One project is PlanetQuest at: Visit their site and look into the possibilities of helping measure the transit of an extrasolar planet across its primary star's disk.