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Entering orbit…
Habitability
22/ 100
Extremely Harsh
Kepler-186 d rendered in TerraForge from its measured mass, orbit and star

Kepler-186 d

Also written Kepler-186d, Kepler 186d, Kepler 186 d

Rocky Terrestrial580 light years awayFound 2014
Mass
2.54 × Earth
Radius
1.40 × Earth
Gravity
1.30 g
Surface (est.)
469 K
Year
13.3 days
From Earth
581 ly
Mass
2.54 × Earth
Radius
1.40 × Earth
Gravity
1.30 g
Surface (est.)
469 K
Year
13.3 days
From Earth
581 ly

Kepler-186 system

Type
K-type (Orange)
Spectral type
M1
Temperature
3,788 K
Radius
0.472 ☉
Mass
0.478 ☉
Planets
5
Luminosity
0.0412 ☉

Published by the NASA Exoplanet Archive. This world’s temperature and habitability score are computed from this star’s measured luminosity, not from a stand-in for its class.

Kepler-186 b0.034 AU1.2 M⊕
Kepler-186 c0.045 AU2.1 M⊕
Kepler-186 d0.078 AUYou are here2.5 M⊕
Kepler-186 e0.11 AU2.1 M⊕
Kepler-186 f0.43 AU1.7 M⊕
Habitable zone

Star and planets drawn to scale: the star is 37 times as wide as Kepler-186 d, so only its edge is in view. Orbits spaced as in the star system view.

Rocky Terrestrial, likely · its density could also fit a sub-Neptune

Kepler-186 d, from the NASA Exoplanet Archive (found 2014). Measured: 2.54 Earth masses, 0.0781 AU, a 3788 K K-type star. Composition inferred from a measured bulk density of 0.93x Earth's at this size, suggesting roughly 16% water/ice by mass, with a day locked to its 13.3-day year, as anything orbiting this close would be.

Surface. Rocky surface with impact craters, possible volcanic features

Rocky Terrestrial
Life unlikely — too hot for liquid waterHigh Activity
Kepler-186 d is dominated by silicate (21.4%) and iron (10.8%) content, forming a rocky terrestrial body.
Rocky terrestrial planets are primarily composed of silicate rocks and metals. They're the most common type of small planet in the universe.
Classification Criteria:
✓ Silicon: 21.4% + Iron: 10.8% + Magnesium: 3.0%✓ Mass: 2.5x Earth (terrestrial range)

Reading Kepler-186 d’s atmosphere

Dominant elements: O, Si, H, Fe, N, CThis is what a telescope would measure while Kepler-186 d crosses in front of its star: starlight passes through the atmosphere and spreads into a rainbow band. Each dark line marks a wavelength the atmosphere absorbed.Every element absorbs its own signature wavelengths — hydrogen always darkens the same two spots, calcium another pair, and so on. Astronomers match the lines in a real spectrum against a library of these signatures to say what an atmosphere is made of, light-years away, without ever visiting. A deeper line generally means more of that element is present.Kepler-186 d sits about 581 light-years away, found by the transit method. Most catalogued distances trace back to parallax: as Earth orbits the Sun, a nearby star appears to shift very slightly against the distant background stars, and the size of that shift gives its distance directly.
Further reading
ExoplanetsSara Seager (editor)The field's standard reference: how planets are found, how they form, and what their atmospheres are made of.The Planet FactoryElizabeth TaskerHow planets are made, and why so few of them come out like Earth.The Little Book of ExoplanetsJoshua WinnHow these worlds are found, and what a measurement can honestly tell us.Exoplanets: Diamond Worlds, Super Earths, Pulsar PlanetsMichael Summers & James TrefilThe strange end of the catalogue — carbon worlds, molten rock, planets orbiting dead stars.
As an Amazon Associate I earn from qualifying purchases — if you buy through these links, TerraForge may receive a small commission at no extra cost to you.
Habitability ScoreExtremely Harsh
22
Contributing Factors
temperature11
Extremely hot - hostile to known life forms
atmosphere42

Thin CO₂ and nitrogen atmosphere

Nitrogen atmosphere provides protection but not breathable (partially stripped by slow rotation)
water64
Abundant water - likely as steam
magnetic Field30
No magnetic field - vulnerable to solar radiation
geology90
Active geology recycles nutrients and drives carbon cycle
Organic Chemistry80
Core organic elements (CHNO) present
rotation30
Very slow rotation - days and nights each last several Earth days, bringing extreme temperature swings

Physical Properties

Mass
2.54x Earth (1.52e+25 kg)
Radius
1.36x Earth (8,693 km)
This planet: 1.36× Earth radiusEarth: 1× (baseline)
Surface Gravity
1.36x Earth (13.4 m/s²)
Surface Temperature
469 K (196 °C / 385 °F)
Rotation Period
319.2 hours/day (slower than Earth)
This planet: 319 h/dayEarth: 24 h/day

Elemental Composition

A dark ringed planet hanging over the horizon of a rocky moon, its rings lit by a distant sun

New: Stand on Your Moons 🌒

A planet's surface view isn't the only ground any more. Press the surface button on a planet with moons and it asks where to stand: the planet itself, or any moon still in orbit, each tagged with what it became — ocean, ice, carbon, volcanic. Every moon gets its own ground and sky from its own physics: airless rock under a black sky, ice cracked by geysers over a hidden sea, sulfur plains shaking with eruptions, or orange haze you can't see the sun through. And hanging over the horizon, there's the planet you built.

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