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Planet profiles

Kepler-186 e

Rocky Terrestrial · 580 light-years away · Last reviewed October 15, 2026

Kepler-186 e rendered in TerraForge from its measured mass, orbit and star
TerraForge's rendering of Kepler-186 e, generated by our physics engine from its measured mass, size, orbit and star. An illustration of what the science suggests, not a photograph.
TerraForge classification
Rocky Terrestrial
Host star
Kepler-186 (M1)
Distance
580 light-years
Orbit
22.4 days
Mass
2.15 × Earth
Radius
1.27 × Earth
Discovered
2014, transit

Figures from the NASA Exoplanet Archive. The classification is TerraForge’s, from its physics model.

Kepler-186 e is the next planet in from Kepler-186 f, the first Earth-sized planet found in a star's habitable zone. Kepler-186 is a red dwarf about half the Sun's size, about 580 light-years away, with five known planets, all roughly the size of Earth. Kepler-186 e is about 1.3 times Earth's width and orbits every 22.4 days.

NASA's Kepler space telescope found all five by catching the small dips in starlight as each crossed the star. In 2014 a team led by Elisa Quintana announced the fifth and outermost, Kepler-186 f, and placed it in the habitable zone, the range of distances where liquid water could last on a surface.

Kepler-186 e shows how narrow that zone is. It is only a little closer to the star than f, but according to the NASA Exoplanet Archive it receives about 3.6 times the light Earth gets from the Sun, too much for liquid water, while f receives about a third. Its mass has not been measured; the archive's figure of about 2 Earth masses is an estimate from its size, so whether it is rocky is not known.

Sources

  1. An Earth-sized Planet in the Habitable Zone of a Cool Star — arXiv (Science)
  2. Kepler-186 Overview — NASA Exoplanet Archive
A banded gas giant with four moons in different colors: a yellow sulfur moon, two rust-red rock moons and a blue water moon

New: Choose What Your Moons Are Made Of 🌙

Every moon used to be grey rock, white ice or blue ocean, decided for you. Now each one has a "Made of" choice in the builder's Moons tab — silicate rock, iron, water ice, carbon, sulfur, or nitrogen and methane ice — and the physics decides what that becomes. Put water ice too close to the star and it boils off to bare rock. Put sulfur where a neighbouring moon keeps it tidally flexed and it erupts in Io's yellows. Give a Titan-sized moon nitrogen ice far from the sun and it wraps itself in haze. Hang a water moon about the mass of Earth off a giant planet in the habitable zone and it can hold air and open seas — scored for life on the same scale as a planet, with a day as long as its orbit. A tint slider nudges the colour, but only as far as that material could really go.

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