In 2009, NASA launched the Kepler Space Observatory to monitor the brightness of over 140,000 stars in a small section of space. The result of the mission will be a record of extra-solar planets as they transit, or move, across their home stars, causing the brightness to dip. Astronomer David Charbonneau explains.

Image courtesy of NASA Goddard Photo and Video; Recorded June 2010; Posted April 2011