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Entering orbit…
Habitability
22/ 100
Extremely Harsh

GJ 15 A b

Rocky TerrestrialExtremely Harsh12 light years awayFound 2014

GJ 15 A b, from the NASA Exoplanet Archive (found 2014). Measured: 3.03 Earth masses, 0.072 AU, a 3607 K M-type star. Composition inferred from a measured bulk density of 0.81x Earth's, which is rock and iron, with a day locked to its 11.4-day year, as anything orbiting this close would be. Note: TerraForge comes out at 405 K against the archive's 550 K, because it models stars by spectral class, and GJ 15 A is not an average M-type.

Host star

GJ 15 A

Type
M-type (Red Dwarf)
Spectral type
M1
Temperature
3,607 K
Radius
0.38 ☉
Mass
0.38 ☉
Known planets
2, including this one
Luminosity
0.0221 ☉

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

High 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: 3.0x 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.
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
temperature15
Extremely hot - hostile to known life forms
atmosphere42
Nitrogen atmosphere provides protection but not breathable (partially stripped by slow rotation)
water44
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
3.03x Earth (1.81e+25 kg)
Radius
1.45x Earth (9,219 km)
This planet: 1.45× Earth radiusEarth: 1× (baseline)
Surface Gravity
1.45x Earth (14.2 m/s²)
Surface Temperature
405 K (132 °C / 270 °F)
Rotation Period
273.6 hours/day (slower than Earth)
This planet: 274 h/dayEarth: 24 h/day

Orbital Environment

Star Type
M-type (Red Dwarf)
Distance from Star
0.07 AU (10.8 million km)
Orbital Period
13 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

New: The Exoplanet Catalog 🔭

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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