Kepler-186 d
Kepler-186 d is a super-Earth orbiting the M1 star Kepler-186 in the constellation Cygnus. It lies about 579 light-years from Earth and was discovered in 2014 using the transit method.
How Big Is Kepler-186 d?
Kepler-186 d has a radius of 1.40 times that of Earth.
Is Kepler-186 d in the Habitable Zone?
Kepler-186 d orbits inside the inner edge of the habitable zone of Kepler-186. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-186: 0.165–0.423 AU (conservative: 0.209–0.401 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-186 d — one full orbit around Kepler-186 — lasts 13.3 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.078 AU — closer to its star than Mercury is to the Sun.
How Was Kepler-186 d Discovered?
Kepler-186 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-186 d?
Kepler-186 d is 579.2 light-years (177.6 parsecs) from Earth. Light arriving here tonight left the planet around the year 1447. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 10,193,920 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-186 d scores 0.46, ranking #306 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-186
Kepler-186
- Spectral type
- M1
- Surface temperature
- 3,788 K (Sun: 5,772 K)
- Mass
- 0.48 M☉
- Radius
- 0.47 R☉
- Luminosity
- 0.0412 L☉
- Age
- 4.0 billion years (Sun: 4.6)
The Kepler-186 Planetary System
Kepler-186 d is one of 5 known planets in the Kepler-186 system. Its siblings:
- Kepler-186 b (Terrestrial)
- Kepler-186 c (Terrestrial)
- Kepler-186 e (Super Earth)
- Kepler-186 f (Terrestrial)
Kepler-186 d — Complete Data
| Radius | 1.400 Earth radii (0.125 Jupiter radii) |
|---|---|
| Orbital period | 13.34 days |
| Orbital distance | 0.078 AU |
| Earth Similarity Index | 0.46 |
| Distance from Earth | 579.2 light-years (177.6 parsecs) |
| Constellation | Cygnus |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2014 |
Data: NASA Exoplanet Archive, last updated 2014-05-14. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-186 d
Is Kepler-186 d habitable?
No — Kepler-186 d orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-186 d?
Kepler-186 d is about 579 light-years from Earth in the constellation Cygnus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 10,193,920 years to get there.
How big is Kepler-186 d compared to Earth?
Kepler-186 d has 1.40 times the radius of Earth.
How long is a year on Kepler-186 d?
One orbit around Kepler-186 takes 13.3 Earth days — short enough that 27 of its years would fit into one Earth year.
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