Imaging with adaptive optics and coronographs for exoplanet research

Direct imaging is particularly valuable for characterization of exoplanets: orbits are measured, planet sizes are constrained from brightness measurements, and the planet light can be decomposed in wavelength, polarization state, and time to reveal atmosphere composition and physical properties (pressure, temperature). Images can also reveal multiple planets and map dust distribution to reveal the dynamical evolution and history of exoplanetary systems. Provided that starlight can be canceled with a coronagraph to reduce contamination, the measurements can be of high quality and take full advantage of the sensitivity offered by current and future large ground-based telescopes. Adaptive optics and starlight suppression techniques are essential to deliver the high-contrast imaging performance required for exoplanet imaging. While a few young warm giant planets have been imaged from the ground, the vast majority of exoplanets, including habitable planets, remains beyond current AO systems capabilities. Yet, thanks to rapid ongoing developments in adaptive optics and coronagraphy, and the upcoming generation of 30-m class giant segmented mirror telescopes (GSMTs), direct imaging is poised to reveal and characterize a large number of planets, including nearby habitable planets.