Physics & Astronomy Professor Bruce Macintosh, Stanford University: "Direct Imaging of Extrasolar Planets"

Almost 4,000 extrasolar planets are now known, but almost all have been detected through so-called indirect methods-- measuring the parent star’s Doppler shift or brightness variations. Direct detection refers to spatially separating the planet’s light from that of the star. It is extremely challenging-- Jupiter in our solar system is 10^-9 the luminosity of the sun --but allows observations of planets inaccessible to other methods, particularly the outer parts of target systems, and allows spectral acharacterization of a planet’s atmospheric properties.

I will discuss the optical physics that makes direct detection challenging, and the techniques-- adaptive optics, coronagraphy, and image processing --that can overcome these challenges. To date, direct detection has been successful for young Jupiter-like planets, and I will show highlights of those discoveries. Finally, I will review future prospects for instruments on ground-based extremely large telescopes, or dedicated space missions with coronagraphs or formation-flying star shades which may reach the level of sensitivity needed to detect Earth-like planets around nearby stars.