Exoplanet Measurement

An exoplanet is a planet that orbits a distant star (a star other than our sun). We can detect exoplanets by a variety of methods. One method is to measure the amount of light blocked by the planet.

In this project, we use a light bulb and a light sensor to simulate exoplanet detection.


  • Light bulb
  • A room that can be made dark
  • Large plastic beads (multiple sizes)
  • String
  • Digital light sensor (TSL2561)
  • Arduino with Grove shield
  • Computer and USB cable


  1. Place a bead on the string.
  2. Tie the string to something placed above the light bulb (you could use a shelf or ring stand).
  3. Connect the light sensor to an I2C plug on your Arduino.
  4. Connect the Arduino to the computer using the USB cable.
  5. In the Sensor Plotter, add a digital light sensor (TSL2561).
  6. Observe how the light sensor values change as you cover it with your hand.
  7. Turn off overhead lights and cover any windows, so that the only light is from your experiment light bulb.
  8. Spin the plastic bead around the bulb.
  9. You may need to try different distances between the bulb and the light sensor to get good readings.


  • Can you see changes in the light level as the exoplanet (bead) passes in front of its star (the bulb)?
  • What differences do you see if the exoplanet is orbiting quickly or slowly?
  • Can you estimate the exoplanet's orbital period (the amount of time it takes for the exoplanet to circle the star)?
  • What if you change the size of the exoplanet (using different sizes of beads)?
  • How small can it be before you can no longer detect it?