About this world
Kepler-138 e is an Earth-sized planet orbiting Kepler-138, a cool red dwarf (type M1V) 218 light-years from Earth. It is about 0.8 times the size of Earth (its size estimated from its mass) and holds 0.43 Earth masses. It completes an orbit every 38.2 days at 0.18 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 292 K (19 °C): too cold for liquid water on its surface. By the "cosmic shoreline", its star has probably stripped its atmosphere away, leaving bare rock.
It was discovered in 2022 by timing variations with Multiple Observatories. Pulsar, eclipse or transit timings drift as an unseen companion tugs on them. Kepler-138 has 4 known planets; the others are Kepler-138 b, Kepler-138 c and Kepler-138 d.