Kepler-31 d
Kepler-31 d is a super-Earth orbiting Kepler-31 in the constellation Cygnus. It lies about 5,429 light-years from Earth and was discovered in 2014 using the transit method.
How Big Is Kepler-31 d?
Kepler-31 d has a radius of 3.90 times that of Earth. Its mass is 2,161 times that of Earth.
Is Kepler-31 d in the Habitable Zone?
Kepler-31 d orbits inside the inner edge of the habitable zone of Kepler-31. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-31: 1.065–2.479 AU (conservative: 1.349–2.351 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-31 d — one full orbit around Kepler-31 — lasts 87.6 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.400 AU — comparable to the inner Solar System.
How Was Kepler-31 d Discovered?
Kepler-31 d was discovered in 2014 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-31 d?
Kepler-31 d is 5,429.3 light-years (1,664.6 parsecs) from Earth. Light arriving here tonight left the planet about 5,429 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 95,555,680 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-31 d scores 0.27, ranking #2,702 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-31
Kepler-31
- Surface temperature
- 6,340 K (Sun: 5,772 K)
- Mass
- 1.21 M☉
- Radius
- 1.22 R☉
The Kepler-31 Planetary System
Kepler-31 d is one of 3 known planets in the Kepler-31 system. Its siblings:
- Kepler-31 b (Neptune-like)
- Kepler-31 c (Neptune-like)
Kepler-31 d — Complete Data
| Radius | 3.900 Earth radii (0.348 Jupiter radii) |
|---|---|
| Mass | 2,161.24 Earth masses (6.800 Jupiter masses) |
| Orbital period | 87.65 days |
| Orbital distance | 0.400 AU |
| Earth Similarity Index | 0.27 |
| Distance from Earth | 5,429.3 light-years (1,664.6 parsecs) |
| Constellation | Cygnus |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2014 |
Data: NASA Exoplanet Archive, last updated 2016-03-23. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-31 d
Is Kepler-31 d habitable?
No — Kepler-31 d orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-31 d?
Kepler-31 d is about 5,429 light-years from Earth in the constellation Cygnus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 95,555,680 years to get there.
How big is Kepler-31 d compared to Earth?
Kepler-31 d has 3.90 times the radius of Earth and about 2,161 times its mass.
How long is a year on Kepler-31 d?
One orbit around Kepler-31 takes 87.6 Earth days.
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