A new Periodic Table of Exoplanets guides scientists and science fans alike through over 3,700 known exoplanets, including those that may host life. To organize the thousands of worlds identified since the first exoplanet was discovered in 1992, astronomer Abel Méndez of the Planetary Habitability Laboratory at the University of Puerto Rico created a chart that sorts the exoplanets into 18 distinct categories. “We know of over 3,700 planets around other stars. They are very diverse,” Méndez said in an interview with Gizmodo. “We can roughly classify them by their size and temperature. Only warm planets with the right size, similar to Earth, might provide some of the conditions for extraterrestrial life.”
At the most general level, exoplanets, or planets beyond our solar system, are categorized based on distance from the star around which they orbit and their temperature. This places them in one of three zones: Hot Zone, Warm Zone, or Cold Zone. The exoplanets are also distinguished by size and composition (rocky “terran” planets vs. gas giants like Neptune and Jupiter). As in the actual periodic table, each exoplanet category has a number assigned to it, which indicates how many of a particular kind of planet have been discovered.
According to the Periodic Table of Exoplanets, there are 53 known exoplanets with the appropriate size, temperature and features such as liquid water and a stable atmosphere to potentially host life as we know it. “Unfortunately, we don’t know yet if they also have the right amount of water (e.g. oceans) or the right atmosphere for life too,” said Méndez. As for the disproportionate number of hot planets on the Table, Méndez explained that this is due to the relative ease of discovery for hot planets and not necessarily because there are more of them.
At the top right corner of the Table, a chart indicates the number of stellar systems and the number of known exoplanets for each system. To Méndez, the possibilities are endless. “I’m overwhelmed by the number and diversity of planets in the stars around us. So many places to explore in our own Solar System, but much more is waiting for us beyond,” Méndez told Gizmodo. “I won’t be very surprised by another planet with life, Earth is the example that this is possible. I will be more surprised by something we haven’t seen before.”