Kepler-139 d
Kepler-139 d is a super-Earth orbiting Kepler-139 in the constellation Lyra. It lies about 1,275 light-years from Earth and was discovered in 2023 using the transit method.
How Big Is Kepler-139 d?
Kepler-139 d has a radius of 1.70 times that of Earth. Its mass is 4.7 times that of Earth, giving it a density of 5.27 g/cm³ — comparable to rocky planets like Earth (5.51 g/cm³).
Is Kepler-139 d in the Habitable Zone?
Kepler-139 d orbits inside the inner edge of the habitable zone of Kepler-139. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-139: 0.924–2.189 AU (conservative: 1.171–2.076 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
See the full interactive habitable-zone view in the Exoplanet Explorer app ›
Orbit and Year Length
A year on Kepler-139 d — one full orbit around Kepler-139 — lasts 7.31 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.076 AU — closer to its star than Mercury is to the Sun.
How Was Kepler-139 d Discovered?
Kepler-139 d was discovered in 2023 using the transit method, with observations from Kepler.
The transit method watches a star for the tiny, regular dip in brightness that occurs when a planet crosses in front of it. The depth and timing of these dips reveal the planet's size and orbital period.
How Far Away Is Kepler-139 d?
Kepler-139 d is 1,275.4 light-years (391.0 parsecs) from Earth. Light arriving here tonight left the planet about 1,275 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 22,447,040 years to make the journey.
Earth Similarity Index
The Earth Similarity Index (ESI) scores how physically similar a planet is to Earth, from 0 to 1, based on radius, density, escape velocity and surface temperature. Kepler-139 d scores 0.28, ranking #2,353 of 5,565 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-139
Kepler-139
- Surface temperature
- 5,594 K (Sun: 5,772 K)
- Radius
- 1.30 R☉
The Kepler-139 Planetary System
Kepler-139 d is one of 5 known planets in the Kepler-139 system. Its siblings:
- Kepler-139 b (Mini Neptune)
- Kepler-139 c (Sub Neptune)
- Kepler-139 e (Cold Gas Giant)
- Kepler-139 f (Neptune-like)
Kepler-139 d — Complete Data
| Radius | 1.695 Earth radii (0.151 Jupiter radii) |
|---|---|
| Mass (best estimate) | 4.66 Earth masses |
| Density | 5.27 g/cm³ (Earth: 5.51) |
| Orbital period | 7.31 days |
| Orbital distance | 0.076 AU |
| Earth Similarity Index | 0.28 |
| Distance from Earth | 1,275.4 light-years (391.0 parsecs) |
| Constellation | Lyra |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2023 |
Data: NASA Exoplanet Archive, last updated 2024-02-21. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-139 d
Is Kepler-139 d habitable?
No — Kepler-139 d orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-139 d?
Kepler-139 d is about 1,275 light-years from Earth in the constellation Lyra. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 22,447,040 years to get there.
How big is Kepler-139 d compared to Earth?
Kepler-139 d has 1.70 times the radius of Earth and about 4.7 times its mass.
How long is a year on Kepler-139 d?
One orbit around Kepler-139 takes 7.3 Earth days — short enough that 50 of its years would fit into one Earth year.
Explore Kepler-139 d in the app
Browse, filter and compare 6,000+ exoplanets on iPhone, iPad and Apple Watch — with habitable-zone views, widgets and offline data.
