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Entering orbit…
Habitability
56/ 100
Marginal
TRAPPIST-1 c rendered in TerraForge from its measured mass, orbit and star

TRAPPIST-1 c

Also written TRAPPIST-1c, TRAPPIST 1c, TRAPPIST 1 c

Earth Like40 light years awayFound 2016
Mass
1.31 × Earth
Radius
1.10 × Earth
Gravity
1.08 g
Surface (est.)
347 K
Year
2.4 days
From Earth
40.4 ly
Mass
1.31 × Earth
Radius
1.10 × Earth
Gravity
1.08 g
Surface (est.)
347 K
Year
2.4 days
From Earth
40.4 ly

TRAPPIST-1 system

Type
M-type (Red Dwarf)
Spectral type
M8.0 V
Temperature
2,566 K
Radius
0.119 ☉
Mass
0.0898 ☉
Planets
7
Luminosity
5.53e-4 ☉

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.

TRAPPIST-1 b0.011 AU1.4 M⊕
TRAPPIST-1 c0.016 AUYou are here1.3 M⊕
TRAPPIST-1 d0.022 AU0.4 M⊕
TRAPPIST-1 e0.029 AU0.7 M⊕
TRAPPIST-1 f0.038 AU1.0 M⊕
TRAPPIST-1 g0.047 AU1.3 M⊕
TRAPPIST-1 h0.062 AU0.3 M⊕
Habitable zone

Star and planets drawn to scale: the star is 12 times as wide as TRAPPIST-1 c, so only its edge is in view. Orbits spaced as in the star system view.

TRAPPIST-1 c is the second of seven Earth-sized planets around TRAPPIST-1, a small, cool red dwarf about 40 light-years away. It orbits every 2.42 days and receives about twice the light Earth gets from the Sun, roughly what Venus receives. That made it a natural test of whether a Venus-like planet around a red dwarf can keep a thick atmosphere.

Surface. Rocky surface with continents, oceans, and active plate tectonics. Diverse biomes if life present.

✓ Conditions could support life. This planet’s modelled conditions could support biological processes: stable temperatures, liquid water and the chemistry life as we know it needs. That makes life possible, not present.

Earth Like
Life possibleMagnetic FieldModerate Activity
TRAPPIST-1 c has a balanced composition with all CHNOPS elements, proper mass (1.3x Earth), and sits in the habitable zone at 0.02 AU.
Earth-like planets have the perfect combination of composition, temperature, mass, and magnetic field to potentially support complex life as we know it.
Classification Criteria:
✓ All CHNOPS elements present (C, H, N, O, P, S)✓ Mass: 1.3x Earth (0.5-2.0x range)✓ Temperature: 347K (250-320K range)✓ Magnetic field present✓ Distance: 0.02 AU (habitable zone)

Reading TRAPPIST-1 c’s atmosphere

Dominant elements: O, Si, Fe, N, H, CThis is what a telescope would measure while TRAPPIST-1 c 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.TRAPPIST-1 c sits about 40 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.Envisioning ExoplanetsMichael CarrollWhat these worlds might look like from the ground, painted from the same measurements this page renders.
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 ScoreMarginal
56
Contributing Factors
temperature35
Hot - near boiling, only heat-loving microbes would thrive
atmosphere100

Nitrogen-oxygen atmosphere with trace CO₂, water vapor, and argon

Nitrogen-oxygen atmosphere - breathable and protective
water50
Limited water content
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
1.31x Earth (7.82e+24 kg)
Radius
1.09x Earth (6,971 km)
This planet: 1.09× Earth radiusEarth: 1× (baseline)
Surface Gravity
1.09x Earth (10.7 m/s²)
Surface Temperature
347 K (74 °C / 164 °F)
Rotation Period
58.1 hours/day (slower than Earth)
This planet: 58 h/dayEarth: 24 h/day

Time Dilation

Clocks run 8.9 seconds per year slower than deep space — about 12 minutes over a lifetime

Elemental Composition

How TerraForge built this world

TRAPPIST-1 c, from the NASA Exoplanet Archive (found 2016). Measured: 1.31 Earth masses, 0.0158 AU, a 2566 K M-type star. Composition inferred from a measured bulk density of 0.98x Earth's, which is rock and iron, with a day locked to its 2.4-day year, as anything orbiting this close would be.

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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