The quest to find life beyond Earth has led to the discovery of two new planetary systems. One of them harbors three planets that are Earth-sized. But it does not necessarily mean that these planets are also habitable or have conditions necessary to support life.
The first exoplanetary system is located about 160 light years from Earth. The system features a red dwarf star called K2-239 and at least three rocky planets with the same size as the Earth. These planets are orbiting around the star every 5.2, 7.8 and 10.1 days.
The other planetary system also has a red dwarf star surrounded by two super-Earth-like planets. The planets around red dwarf K2-240 are about twice the size of Earth. All these planets apparently do not reside in their stars’ habitable zone as they are orbiting very close to their red dwarfs. The habitable zone is an orbital distance where a rocky planet with an atmosphere could have liquid water on its surface.
The atmospheric temperatures around red stars are 3,450 and 3,800 K respectively. This is almost half the temperature of the sun. Researchers estimate that all newly discovered planets will have temperature tens of degrees higher than that of Earth due to the strong radiation they receive in close orbits to their stars.
Researchers made this discovery by using data collected by the K2 mission of NASA’s Kepler satellite. Kepler is the first NASA mission capable of detecting Earth-size planets, using the transit method or tiny dips in the brightness of a star when a planet crosses in front of it.
Researchers are planning to conduct follow-up studies using NASA’s upcoming James Webb Space Telescope, launching in 2020. With much greater sensitivity, James Webb will characterize the composition of these planets’ atmosphere and other key factors in assessing their habitability.