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Entering orbit…
Habitability
30/ 100
Extremely Harsh

LP 791-18 d

Rocky TerrestrialExtremely Harsh86 light years awayFound 2023

LP 791-18 d, from the NASA Exoplanet Archive (found 2023). Measured: 0.91 Earth masses, 0.0199 AU, a 2960 K M-type star. Composition inferred from a measured bulk density of 0.83x Earth's, which is rock and iron, with a day locked to its 2.8-day year, as anything orbiting this close would be.

Host star

LP 791-18

Type
M-type (Red Dwarf)
Spectral type
M(6.1 +/- 0.7) V
Temperature
2,960 K
Radius
0.182 ☉
Mass
0.139 ☉
Known planets
3, including this one
Luminosity
2.30e-3 ☉

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

Magnetic FieldModerate 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: 0.9x 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
30
Contributing Factors
temperature15
Extremely hot - hostile to known life forms
atmosphere70
Nitrogen atmosphere provides protection but not breathable
water38
Limited water content - likely as steam
magnetic Field100
Magnetic field provides radiation protection
geology90
Active geology recycles nutrients and drives carbon cycle
Organic Chemistry80
Core organic elements (CHNO) present
rotation65
Slow rotation - significant day/night temperature variations, but life can adapt

Physical Properties

Mass
0.91x Earth (5.43e+24 kg)
Radius
0.97x Earth (6,174 km)
This planet: 0.97× Earth radiusEarth: 1× (baseline)
Surface Gravity
0.97x Earth (9.5 m/s²)
Surface Temperature
438 K (164 °C / 328 °F)
Rotation Period
66.0 hours/day (slower than Earth)
This planet: 66 h/dayEarth: 24 h/day

Orbital Environment

Star Type
M-type (Red Dwarf)
Distance from Star
0.02 AU (2.98 million km)
Orbital Period
2 days
Time Dilation
Clocks run 7.0 seconds per year slower than deep space — about 9 minutes over a lifetime

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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