Kepler-138 d — 1.5 times Earth's width, about Earth-sized — probably rocky; its year lasts 23 days; about 72 °C, between freezing and boiling; found in 2014 by transit.
Kepler-138 c — 1.5 times Earth's width, about Earth-sized — probably rocky; its year lasts 14 days; about 140 °C, hotter than boiling water; found in 2014 by transit.
Kepler-138 b — 0.6 times Earth's width, smaller than the Earth; its year lasts 10 days; about 180 °C, hotter than boiling water; found in 2014 by transit.
Kepler-138 e — 0.8 times Earth's width (estimated from its mass, not measured), about Earth-sized — probably rocky; its year lasts 38 days; about 19 °C, between freezing and boiling; found in 2022 by transit timing variations.
NASA Exoplanet Archive, Planetary Systems Composite Parameters (fetched 2026-11-02). Composite values: where a planet's size or mass was not measured, the archive estimates it from the other.
This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with NASA under the Exoplanet Exploration Program.