Radius and Volume of Exoplanets

This activity, from the Royal Observatory Greenwich, uses data from NASA’s Kepler space probe to determine the size of an exoplanet, and provides students with an insight into the advantages and disadvantages of the transit method of exoplanet detection.

A classroom discussion, before the activity, illustrates the principle behind the transit method used to detect exoplanets orbiting distant stars. Just as in a solar eclipse or a transit of Venus, an object moving in front of a star blocks some fraction of its starlight. The resulting graph of periodic variation of brightness over time – a light curve – contains enough information to obtain the orbital period and size of an exoplanet. The student worksheets provide two light curves from NASA’s Kepler probe.