Direct Detection of Exoplanets

Invited review at the "Protostars and Planets V" Conference, October 24−28, 2005, Hilton Waikoloa Village, Hawai'i. Proceedings of the PPV Conference, in press, B. Reipurth and D. Jewitt Eds.Direct detection of exoplanets from the ground is now within reach of existing astronomical instruments. Indeed, a few planet candidates have already been imaged and analyzed and the capability to detect (through imaging or interferometry) young, hot, Jupiter-mass planets exists. We present here an overview of what such detection methods can be expected to do in the near and far term. These methods will provide qualitatively new information about exoplanets, including spectroscopic data that will mature the study of exoplanets into a new field of comparative exoplanetary science. Spectroscopic study of exoplanet atmospheres promises to reveal aspects of atmospheric physics and chemistry as well as internal structure. Astrometric measurements will complete orbital element determinations partially known from the radial velocity surveys. We discuss the impact of these techniques, on three different time scales, corresponding to the currently available instruments, the new ``Planet Finder'' systems under development for 8 to 10-m telescopes, foreseen to be in operation in 5 to 10 years, and the more ambitious but more distant projects at the horizon of 2020