Algebraic Equations: Transit Tracks -- Finding Habitable Planets
A picture of transit light curves

Featured Lesson(s)

Investigation: Transit Tracks [PDF 1.43 MB]



Essential Question

How can we use algebra concepts and Newton’s third law to find planets in outer space that could be habitable?


As the Kepler Mission surveys our region of the Milky Way galaxy, it discovers hundreds of Earth-size and smaller planets that are in or near what is called the habitable zone. As Kepler gathers light curve data from stars, it detects decreases in brightness indicating a planet passing in front of the star.


In this activity, students will investigate light curve data gathered by Kepler. They will use the data to determine the period, orbital distance and size of the planet. By using Newton’s third law to find orbital distance and drop in brightness to find planet size, students will compare these Kepler planets to planets in our own solar system.


Transit Tracks includes a background section titled “Account of Jeremiah Horrocks’ observations of the Transit of Venus.” This activity comes with educator and student editions. The educator edition has information on optional mathematics extensions possible for your classroom. The option of using an orrery to demonstrate a transit is recommended but optional.

Additional Resources

  Classroom Resources:


  • Videos for Students:
    • The Kepler Mission: This NASA video explains the Kepler Mission. The clip is intended to be shown in the classroom to provide students with a real-world application for the lesson.  
    • Orrery: This classroom video demonstrates the method employed by the Kepler Mission to determine the size and location of planets orbiting a distant star. This demonstration employs a device called an "Orrery."  
    • Exoplanet: This video for the classroom demonstrates a free Web-enabled program that mimics the data received by Kepler and lists all of the planets that have been discovered during its mission. Kids can download this program onto their computers or portable digital devices.



  Related NASA Now Events:

  Connection to NASA:

  Extension Activities:

Professional Development

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Lesson Information

Subject(s) Covered:

 Mathematics: Algebra 2 Science: Physical Science

Topic(s) Covered:

 Mathematics: Data interpretation, simplification of algebraic expressions Science: Kepler's Laws of Motion

Activity Type:

 Student Investigation

Grade Level:


Instructional Objective:

 Students will be able to -- Describe a transit and the conditions when a transit may be seen. -- Describe how a planet's size and distance from its star affects the behavior of transits. -- Interpret graphs of brightness vs. time to deduce information about planet-star systems.

Time to Complete the Activity:

 60-90 minutes

  Materials Needed:

  • Clip-on lamp.
  • Frosted, spherically shaped low-wattage (25 W maximum) bulb.
  • Four beads, various sizes (3-12mm) and colors.
  • Thread of various lengths (20-100cm). For best results, use black thread.
  • “Transit Light Curves” -- one set per group of two to five students.
  • Worksheets: One per student or one per group.
  • Account of Jeremiah Horrocks’ observations of the transit of Venus
  • Optional: light sensor and computer with sensor interface and graphing function.

   National Content Standards:



  • Mathematics:
    • Algebra: Analyze change in various contexts.
    • Connections: Recognize and apply mathematics in contexts outside of mathematics.
    • Data Analysis and Probability: Develop and evaluate inferences and predictions that are based on data.
    • Problem Solving: Solve problems that arise in mathematics and in other contexts.


  • 21st Century Skills: Information, Media and Technology Skills -- Information Literacy.
    • Access and evaluate information.
    • Use and manage information.
  • 21st Century Skills: Learning and Innovation Skills.
    • Communication and Collaboration: Collaborate with others.
    • Critical Thinking and Problem Solving: Reason effectively.


  • Science:
    • Physical science: Motions and forces.
    • Science and technology: Abilities of technological design.
    • Physical science: Interactions of energy and matter.