Over the course of two decades, several thousand planets have been discovered and recorded. Most of these exoplanets look nothing like the planets in our Solar System. Dr. Steffen, a member of the science team for NASA’s Kepler mission, joins us to talk about these discoveries and what we’ve learned from them.

The first planets identified beyond the solar system were shockingly unlike the nine worlds long-known within it. In sorting through the new exoplanets, scientists described them in terms that compared them to Earth's neighbors, dubbing them 'hot Jupiters' or 'super-Earths'. There are also 'hot Earths', terrestrial worlds orbiting their suns in periods less than two days.