HEC: Periodic Table of Exoplanets

These images summarize in eighteen thermal-mass/size categories most of the current confirmed exoplanets and Kepler candidates. They provide a simple scheme to bin and visualize the exoplanets 'zoo' out there. This is not a classification based on composition. The number of exoplanets in each category are shown in the center of each frame. Those potentially habitable are described with more details in the Habitable Exoplanet Catalog (HEC).

Last Update: September 1, 2014

The Periodic Table of Exoplanets divides most of the known exoplanets into six mass/size and three temperatures groups (18 categories total). Exoplanets in the Hot Zone are too close of their parent star to have liquid water. Those in the Warm 'Habitable' Zone have the right distance for liquid water given the right size. Water can only exist as ice for those in the Cold Zone. Mercurians are low mass bodies most likely spherical and atmophere-less, like Mercury and the Moon. Subterrans are comparable to Mars, Terrans to Earth and Venus, and Superterrans are up to 10 times as massive as Earth, a category with no comparable examples in the Solar System. Neptunians are similar in mass to Neptune and Uranus, and Jovians to Jupiter and Saturn, or larger. Not all bodies stated in the objects count in the title are classified in the table due to unknown stellar or planetary parameters.


Figure 1. Current confirmed exoplanets classified into eighteen thermal-mass categories. The number of exoplanets in each category is shown in the center of each frame and as a percent in the lower left. The diagram also shows the number of multiple stellar systems (top right). The most abundant objects of the confirmed exoplanets are hot jovians. ME = Earth masses. CREDIT: PHL @ UPR Arecibo.



Figure 2. Current NASA Kepler exoplanets candidates classified into eighteen thermal-size categories. The number of exoplanets in each category is shown in the center of each frame and as a percent in the lower left. Those already confirmed are shown in the lower right. The diagram also shows the number of multiple stellar systems (top right). The most abundant objects of the Kepler exoplanets are hot superterrans. RE = Earth radii. CREDIT: PHL @ UPR Arecibo.



Figure 3.
 Current Solar System spherical objects (with mass over 10-5 Earth masses) including planets, moons, and dwarf planets classified into eighteen thermal-mass categories. The number of objects in each category is shown in the center of each frame and as a percent in the lower left. The diagram helps as a base for comparison with the tables for exoplanets. The most abundant objects of the Solar System are cold mercurians, also known as icy bodies. ME = Earth masses. CREDIT: PHL @ UPR Arecibo.