About this world
Kepler-438 b is an Earth-sized planet orbiting Kepler-438, a cool red dwarf 639 light-years from Earth. It is about 1.1 times the size of Earth. It completes an orbit every 35.2 days at 0.17 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 288 K (15 °C), which places it in the optimistic habitable zone: the band where liquid water could exist on a rocky surface. By the "cosmic shoreline", it has likely held on to an atmosphere.
It was discovered in 2015 by transit with Kepler. A planet crosses its star and dims it by a tiny, periodic fraction.