The Kepler-138 system contains 3 exoplanets. It is located 218.08 light years away from the solar system.
| Mass | 0.52 solar masses |
| Radius | 0.44 solar radiae |
| Temperature | 3841 kelvin |
| Stellar Metallicity | -0.28 decimal exponent |
| Age | 4.68 billion years |
With a mass below 5 Earth masses, a density of 2.6, and a semi-major axis of 0.076 astronomical units, Kepler-138 b could, potentially, be an ocean world - a planet with no dry land.
| Mass | 0.066 Earth masses |
| Density | 2.600 grams per cubic centimeter |
| Radius | 0.522 Earth radiae |
| Semi-major Axis | 0.076 AU |
| Eccentricity | 0.006 |
| Orbital Period | 10.313 days |
| Discovery Method | Transit |
| Discovery Facility | Kepler |
| Discovery Telescope | 0.95 m Kepler Telescope |
| Discovery Instrument | Kepler CCD Array |
| Discovery Date | 2014-03 |
| Reference | Rowe et al. 2014 |
At 1.972 Earth masses, Kepler-138 c is a so called Super Earth. Super Earths could be terrestrial worlds like Earth, but they could also be ocean worlds or terrestrial worlds wrapped in a substantial atmosphere, in which case some refer to them as Mini Neptunes.
| Mass | 1.970 Earth masses |
| Density | 6.200 grams per cubic centimeter |
| Radius | 1.197 Earth radiae |
| Semi-major Axis | 0.0906 AU |
| Eccentricity | 0.011 |
| Orbital Period | 13.781 days |
| Discovery Method | Transit |
| Discovery Facility | Kepler |
| Discovery Telescope | 0.95 m Kepler Telescope |
| Discovery Instrument | Kepler CCD Array |
| Discovery Date | 2014-03 |
| Reference | Kipping et al. 2014 |
With a mass below 5 Earth masses, a density of 2.1, and a semi-major axis of 0.12781 astronomical units, Kepler-138 d could, potentially, be an ocean world - a planet with no dry land.
| Mass | 0.640 Earth masses |
| Density | 2.100 grams per cubic centimeter |
| Radius | 1.212 Earth radiae |
| Semi-major Axis | 0.12781 AU |
| Eccentricity | 0.027 |
| Orbital Period | 23.088 days |
| Discovery Method | Transit |
| Discovery Facility | Kepler |
| Discovery Telescope | 0.95 m Kepler Telescope |
| Discovery Instrument | Kepler CCD Array |
| Discovery Date | 2014-03 |
| Reference | Kipping et al. 2014 |