Life in the Milky Way: Panel Discussion Wesley A. Traub Chief Scientist, NASA’s Exoplanet Exploration Program Jet Propulsion Laboratory, California Institute of Technology Ozma 50 Workshop, Green Bank, West Virginia 13 Sept. 2010

Our Big Questions for Exoplanets What kind of signs of life should we be looking for? Where and how should we look? What is our strategy for finding signs of life beyond the Solar System? 2Traub Strategies for answering these might come from this meeting. Meanwhile, here are the search methods we are using or considering: - Radial velocity mass, orbit (~400 discovered) - Transitsradius, orbit (~700 discovered) - Gravitational lensingmass, orbit (snapshot) (~handful) - Astrometrymass, orbit (none yet) - Nullingexozodiacal brightness - Direct imagingbrightness, orbit, (~5 discovered); also atmosphere, surface, rotation, temperature, water, oxygen, ozone, carbon dioxide, red edge (land plants), i.e., signs of life.

Three Direct Images To Date 3Traub Ref.: Fomalhaut, Kalas et al., 2009 HR8799, Marois et al., 2009 also Serabyn & Mawet 2010 Beta Pic, Lagrange et al., 2010

Exoplanet prospects, near and far Kepler transits/seismology 500 to 2000 pc distant 156,000 stars 14 to 16 mag 0.24% of sky Expect 400 Earths (1/star) CoRoT transits/seismology 400 to 2000 pc distant ~40,000 stars 13 to 15 mag 0.01% of sky SIM Lite astrometry 5 to 25 pc distant ~70 to 2100 stars 3 to 7 mag 100% of sky Expect 70 Earths (1/star) + TPF-C/O/I direct imaging Color & spectrum all planets Signs of life PLATO transits/seismology pc distant 250,000 stars 10 to 13 mag 8% of sky Expect 400 Earths (1/star) WFIRST gravitational microlensing 1000 to 10,000 pc distant

Prospects for finding and characterizing exoplanets Current missions: CoRoT and Kepler for transits - Telling us frequency of terrestrial planets, from close-in to habitable zones Also: Spitzer (warm) and HST - Giving us transit visible and infrared spectra of giant planets Planned missions: JWST - Possible transit spectra of super-Earth planets Recommended mission: WFIRST for exoplanets (and dark energy) - Gravitational lensing gives mass and snapshot of orbit Future possibility: Exoplanet mission - To be decided around mid-decade, and launched in 2020s, could be coronagraph imager for exoplanet discovery and characterization 5Traub