Characterizing Extrasolar Planets

Sara Seager
Institute for Advanced Study

There are 100 known extrasolar giant planets orbiting single
sun-like stars. Characterizing the planet atmospheres is difficult
because the planet-star contrast is many orders of magnitude and the
planet-star systems cannot be spatially resolved with existing
instruments. Nevertheless, extrasolar planet atmosphere observations
are being attempted in the combined light of the planet-star system
for the class of "close-in" planets---seven times closer to their parent
stars than Mercury is to our sun---that are hot thermally and potentially bright
in reflected light. The first observational success was the detection
of neutral sodium  in the atmosphere of the transiting CEGP HD209458b, and
this has provided the first constraint on model atmospheres. I will present
theoretical atmospheric signatures and existing observational constraints
for the CEGPs. I will also discuss the search for Earth-like planets and
new studies of Earth as an extrasolar planet. I will conclude
with what current and future observations will tell us about extrasolar
planets