"Extrasolar Planets: New Discoveries and Challenges"

During the last decade, over one hundred planets around nearby stars have been discovered using high-resolution spectra to measure stellar velocities at the level of 3 m/s. At first, these surveys surprised astronomers by finding giant planets with orbital periods of just a few days and with orbital eccentricities much larger than found in our solar system. As theorists have struggled to understand the implications of these discoveries, radial velocity surveys have improved their sensitivity to giant planets with orbital periods of several years and less massive planets at smaller distances. This month, there have been multiple announcements of planets with masses as small as Neptune, including one orbiting a star with three other planets. In addition to radial velocity surveys, other techniques for finding planets are beginning to bear fruit. Recently, planet candidates have been discovered with four other techniques, including some with orbital periods as small as 1.2 days. Several projects already underway are expected to dramatically increase the variety and number of known extrasolar planets. I will present an overview of these exciting new discoveries and the new challenges that accompany these discoveries and possibilities.