Exoplanet Transit

This simulation shows how astronomers find planets around other stars by the dip in starlight. Students set the planet radius relative to the star, the orbital period in days and the impact parameter, and watch the light curve build as the planet passes in front. Readouts show the dip depth, period, orbit size and how long the transit lasts. Views include an observer on Earth and the orbit from above. Teachers can use it to connect geometry, area ratios and Kepler's third law to real discoveries.

• Raise Planet radius and read the Dip depth readout, which equals the radius ratio squared.
• Change Orbital period and watch Orbit size a and the spacing between dips change.
• Increase Impact parameter to make the planet cross near the star's edge and shorten Transit lasts.
• Use the Observer on Earth view to see what a telescope would see.
• Switch to Orbit from above to see why only some planets transit.

1. 1Explain how a dip in brightness reveals a planet crossing its star.
2. 2Calculate transit depth from the ratio of planet radius to star radius.
3. 3Relate orbital period to orbit size using Kepler's third law.
4. 4Interpret a light curve to find period and relative size.

Questions teachers ask