NASA's Kepler Space Telescope is one of the most prolific hunters of exoplanets. A new survey catalog introduces 219 candidate planets, 10 of which are about the size of the Earth and in orbit in the habitable zones around their host stars. The latest release brings up the total planet candidates identified by Kepler to 4,034, out of which 2,335 have been verified as exoplanets. Kepler has identified roughly 50 earth sized exoplanet candidates in the habitable zones of their host stars, out of which over 30 have been confirmed.
The survey has also identified two distinct populations of small planets, which could have implications in the search for alien life. The survey indicates that half of the exoplanets have no surface, or that the surface lies beneath a crushingly deep atmosphere. Life as we know it on Earth is less likely to exist on exoplanets with such extreme conditions. The catalog allows scientists to estimate the frequency of Earth sized planets, which will form the basis of efforts to directly image an exoplanet.
Susan Thompson, Kepler research scientist for the SETI Institute in California, and lead author of the catalog study says "This carefully-measured catalog is the foundation for directly answering one of astronomy’s most compelling questions – how many planets like our Earth are in the galaxy?" The Kepler Space Telescope continues to observe the skies. Nasa’s Spitzer Space Telescope discovered seven Earth sized exoplanets in the Trappist-1 system, and Kepler observations were used to figure out the intricate dance in their orbits.