Confirmed exoplanet · Database record + computed analysis
Kepler-138 e
A confirmed world orbiting Kepler-138, 218.1 light-years away.
A sub-Earth
smaller than Earth at 0.80 Earth radii. Worlds this small are hard to detect, so every one is a catch.
The orbit
Its year, one full orbit, takes just 38.2 Earth days.
Temperature and starlight
Its equilibrium temperature (the airless-world estimate) is about 19 °C. In the range where, with the right atmosphere, liquid water is conceivable; a real atmosphere could shift the true surface figure a lot (Earth's equilibrium value is −18 °C, yet we average +15 °C). It receives 1.73 times Earth's starlight, the same order as our own world.
Its sun
Its star is a red dwarf (3,841 K surface), type M1 V: small, dim, flare-prone, and destined to outlive the Sun many times over. It shares the system with 3 other known planets.
How far is that, really?
At 218 light-years, tonight's light from this system left it around the year 1807. A Voyager-speed probe would need roughly 3,858,329 years to get there.
How we found it
It was found through transit timing variations: its gravity nudges a sibling planet's transits early and late, betraying its presence without ever being seen directly. The discovery was announced in 2022 from Multiple Observatories.
Everything above is computed from the archive’s measured values for this planet. Where a quantity is missing, the statement is omitted rather than guessed.
About this record
The measured values come from the NASA Exoplanet Archive, and any missing value has not been determined yet; the Atlas never fills gaps with guesses. More standout worlds: Proxima b, TRAPPIST-1e, K2-18 b, 55 Cancri e, and the detection methods that found them all.