The Planetary Habitability Laboratory (PHL) is now searching for Earth-like worlds. The PHL maintains the Habitable Exoplanets Catalog (HEC) in which exoplanets discoveries are classified and compared according to different habitability metrics. Previously the PHL has not been involved in making the initial exoplanet discoveries. Now, the PHL is using new algorithms based on pattern recognition to search for Earth-like worlds within the NASA Kepler Telescope data.
The idea of an Earth-like planet might suggest a world with oceans, breathable air, or even life. However, astronomers are far from getting this information because exoplanets are very far away for our current instruments. For astronomers the definition of Earth-like planets is limited by what we can measure now, their orbit and size. Any exoplanet around a Sun-like star with a similar orbit and size as Earth is considered an Earth-like world.
The new PHL’s project, Search for Potentially Habitable Exoworlds Resembling Earth (SPHERE), is exploring the NASA Kepler data for Earth-like exoplanets and exomoons. Since October 2012 the NASA Kepler data is publicly available for any research team to explore. Many other teams are using this data to discover exoplanets, including the NASA Kepler Team and scientific community projects such as the Hunt for Exomoons with Kepler and Planet Hunters.
Only a few of the nearly 900 confirmed exoplanets barely fit as candidates for potentially habitable worlds. All of these are superterran worlds (super-Earths) up to two times larger than Earth. Scientists are not confident of how habitable these larger worlds might be as compared to Earth. They are more interested in terran worlds (Earth-size) orbiting in the habitable zone of their star, which are more comparable to Earth.
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