A mysterious exoplanet that astronomers have dubbed K2-18b might be a “super-Earth” that could potentially harbor extraterrestrial life, Phys.org reports. Adding to scientists’ excitement, they’ve recently discovered that this distant body is orbited by yet another Earth-like planet, called K2-18c. The findings were recently published in the journal Astronomy & Astrophysics [PDF].
Discovered in 2015, K2-18b orbits a red-dwarf star named K2-18 in the constellation Leo (about 111 light years from Earth), as does its more recently located counterpart. While both planets have masses similar to Earth, K2-18c probably can’t support life—it’s too close to the star and therefore too hot. K2-18b, on the other hand, is situated in perfect range from K2-18 to have liquid surface water, which all organisms need to live.
Astronomers discovered the exoplanets using the European Southern Observatory’s High Accuracy Radial Velocity Planet Searcher (HARPS) instrument at the La Silla Observatory in Chile. The data they collected also allowed them to calculate the mass and density of K2-18b. According to preliminary findings, the exoplanet is either rocky with an Earth-like gaseous atmosphere, or watery and covered in ice. Further research with NASA’s James Webb Space Telescope (JWST), which launches in spring 2019, will help astronomers determine K2-18b’s true nature.
In addition to revealing K2-18b’s mass, HARPS data also revealed the presence of K2-18c. Discovering an additional exoplanet was still “lucky and equally exciting," even if it probably couldn't support life, said lead author Ryan Cloutier, a Ph.D. student at the University of Toronto Scarborough's Center for Planet Science, according to a news release.