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Entering orbit…
Habitability
23/ 100
Extremely Harsh

K2-129 b

Rocky TerrestrialExtremely Harsh91 light years awayFound 2017

K2-129 b, from the NASA Exoplanet Archive (found 2017). Measured: 1.12 Earth masses, 0.057 AU, a 3459 K M-type star. Composition inferred from a measured bulk density of 1.00x Earth's, which is rock and iron, with a day locked to its 8.2-day year, as anything orbiting this close would be.

Host star

K2-129

Type
M-type (Red Dwarf)
Temperature
3,459 K
Radius
0.36 ☉
Mass
0.36 ☉
Known planets
1 (this one)
Luminosity
0.0148 ☉

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.

Rocky Terrestrial

Moderate Activity
Why is this a Rocky Terrestrial?Your planet is dominated by silicate (25.0%) and iron (12.5%) 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: 25.0% + Iron: 12.5% + Magnesium: 3.8%✓ Mass: 1.1x Earth (terrestrial range)
Further reading
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.Envisioning ExoplanetsMichael CarrollWhat these worlds might look like from the ground, painted from the same measurements this page renders.Imagined LifeJames Trefil & Michael SummersWhat could live on a world like this one: ice shells, supergravity, tidally locked twilight.
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Habitability ScoreExtremely Harsh
23
Contributing Factors
temperature15
Extremely hot - hostile to known life forms
atmosphere70
Nitrogen atmosphere provides protection but not breathable
water43
Limited water content - 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 - extreme temperature swings between eternal day and night sides

Physical Properties

Mass
1.12x Earth (6.69e+24 kg)
Radius
1.04x Earth (6,616 km)
This planet: 1.04× Earth radiusEarth: 1× (baseline)
Surface Gravity
1.04x Earth (10.2 m/s²)
Surface Temperature
412 K (139 °C / 282 °F)
Rotation Period
197.8 hours/day (slower than Earth)
This planet: 198 h/dayEarth: 24 h/day

Orbital Environment

Star Type
M-type (Red Dwarf)
Distance from Star
0.06 AU (8.53 million km)
Orbital Period
9 days

Atmosphere

Thin CO₂ and nitrogen atmosphere

Elemental Composition

O - Oxygen
31.3%
Si - Silicon
25.0%
Fe - Iron
12.5%

Surface Characteristics

Rocky surface with impact craters, possible volcanic features
The TerraForge exoplanet catalog: 5,572 real exoplanets run through the simulation, with a search field and rendered worlds grouped by type

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Every confirmed planet NASA has measured well enough to build — 5,572 of them — is now in here, and none of them arrived with a label. Their real mass, radius, orbit and star go through the same simulation that runs everything you make, and it decides what each one is: gas giant, lava world, ocean, ice. Sixteen come out Earth-like. Find TRAPPIST-1e, stand on its surface, and see what a red dwarf's light actually looks like from the ground.

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