Planetary transits are not only historically significant, they are a key tool for future exploration.  The NASA Kepler mission is looking at more than 100,000 distant stars for periodic dips in brightness that would reveal the presence of habitable planets encircling their parent stars.  Planetarium director Ruth Craft demonstrates how the spacecraft senses the dimming, generates a light curve, and guides astronomers toward candidate star systems.  The Kepler team provides excellent online resources for educators at http://kepler.nasa.gov/education/.  See Transit Tracks, for example, a detailed investigation that parallels this video produced by WNIT public television's Outdoor Elements, with host Evie Kirkwood. 

From WNIT Outdoor Elements, Episode #1003, Segment #3