This talk is by Dimitar Sasselov, and is about the Kepler mission to find exoplanets. Here is a brief bio of Sasslov from this link :
Dimitar Sasselov is an astronomer who explores the interaction between light and matter. He studies, among other things, extrasolar planets, and he's a co-investigator on NASA's Kepler mission, which is monitoring 100,000 stars in a three-year hunt for exoplanets -- including Jupiter-sized giants. Sasselov watches for exoplanets by looking for transits, the act of a planet passing across the face of its star, dimming its light and changing its chemical signature. This simple, elegant way of searching has led to a bounty of newly discovered planets.
Towards the end of the talk he mentions the Pale Blue Dot, a photograph taken of Earth from beyond Saturn's orbit. For a discussin of the Pale Blue Dot see this post.