Exploring the Landscape of Habitable Exoplanets via Their Disk-integrated Colors and Spectra: Indications for Future Direct Imaging Observations

Yuka Fujii (University of Tokyo)

Recent discoveries of exoplanets have implied a number of Earth-size/super-Earth-size exoplanets in so-called habitable zones, which stimulates our expectation for planets harboring life outside the Solar System. While the detection of small planets in the HZ itself is an essential first step, further investigations are needed to know their properties in detail. A key approach is direct detection of their light separated from the host star. Indeed several proposals for direct imaging observations, both space-based and ground-based, are being actively discussed. Even with the aid of such future instruments, however, it is not straightforward to decipher the signals, because the information accessible via astronomical observation is inevitably limited. In particular, exoplanets are point sources to us and only disk-integrated light would be available. In this talk, I discuss the methods to recover the maps of continents, ocean, and/or clouds from the time variation of planetary color caused by spin rotation and/or orbital motion. I also examine the variation of spectral absorption features as a probe of clouds and the water cycle.