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Entering orbit…
Habitability
18/ 100
Uninhabitable

GJ 3138 c

BarrenUninhabitable93 light years awayFound 2017

GJ 3138 c, from the NASA Exoplanet Archive (found 2017). Measured: 4.18 Earth masses, 0.057 AU, a 3717 K K-type star. Composition inferred from a measured bulk density of 0.63x Earth's — too light for bare rock, so a large fraction of water and ice, with a day locked to its 6.0-day year, as anything orbiting this close would be.

Host star

GJ 3138

Type
K-type (Orange)
Spectral type
M0
Temperature
3,717 K
Radius
0.5 ☉
Mass
0.681 ☉
Known planets
3, including this one
Luminosity
0.0450 ☉

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.

Barren

High Activity
Why is this a Barren?Your planet has an unusual composition that doesn't fit standard classifications, or lacks the elements needed for complex geological processes.
Barren worlds can form from uncommon element combinations or may be remnants of larger bodies that lost their atmospheres and volatile materials.
Classification Criteria:
Composition doesn't match standard planet typesMass: 4.2x EarthTemperature: 577K
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 ScoreUninhabitable
18
Contributing Factors
temperature15
Extremely hot - hostile to known life forms
atmosphere70
Nitrogen atmosphere provides protection but not breathable
water24
Abundant water - boiling away, little would be retained
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
4.18x Earth (2.50e+25 kg)
Radius
1.61x Earth (10,263 km)
This planet: 1.61× Earth radiusEarth: 1× (baseline)
Surface Gravity
1.61x Earth (15.8 m/s²)
Surface Temperature
577 K (304 °C / 579 °F)
Rotation Period
143.3 hours/day (slower than Earth)
This planet: 143 h/dayEarth: 24 h/day

Orbital Environment

Star Type
K-type (Orange)
Distance from Star
0.06 AU (8.53 million km)
Orbital Period
6 days
Time Dilation
Clocks run 5.7 seconds per year slower than deep space — about 8 minutes over a lifetime

Atmosphere

Thin CO₂ and nitrogen atmosphere

Elemental Composition

O - Oxygen
41.2%
H - Hydrogen
17.6%
Si - Silicon
11.8%

Surface Characteristics

Barren rocky surface with unusual elemental composition
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