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Entering orbit…
Habitability
0/ 100
Uninhabitable

Reading K2-38 c’s atmosphere

Dominant elements: H, O, Si, Fe, N, CThis is what a telescope would measure while K2-38 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.K2-38 c sits about 629 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.

K2-38 c

Ice GiantUninhabitable629 light years awayFound 2016

K2-38 c, from the NASA Exoplanet Archive (found 2016). Measured: 8.3 Earth masses, 0.0951 AU, a 5731 K G-type star. Composition inferred from a measured bulk density of 0.69x Earth's at this size, suggesting roughly 56% water/ice by mass, with a day locked to its 10.6-day year, as anything orbiting this close would be.

Host star

K2-38

Type
G-type (Yellow (Sun-like))
Spectral type
G2 V
Temperature
5,731 K
Radius
1.06 ☉
Mass
1.03 ☉
Known planets
2, including this one
Luminosity
1.09 ☉

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.

Ice Giant

No life — too hot for liquid waterExtreme Activity
Why is this a Ice Giant?Your planet has moderate mass (8.3x Earth) with significant water, carbon, and nitrogen content, characteristic of ice giants.
Ice giants like Uranus and Neptune have icy interiors with thick atmospheres of hydrogen and helium, but not enough to be classified as gas giants.
Classification Criteria:
✓ Mass: 8.3x Earth (5-20x range)✓ Water/Carbon/Nitrogen rich composition
Further reading
Exoplanets: Diamond Worlds, Super Earths, Pulsar PlanetsMichael Summers & James TrefilThe strange end of the catalogue — carbon worlds, molten rock, planets orbiting dead stars.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.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 ScoreUninhabitable
0
Contributing Factors
temperature0
Inferno world - temperatures exceed all possibility of life
atmosphere18
Hydrogen-rich atmosphere typical of gas giants (partially stripped by slow rotation)
water15
No solid surface — any water is locked in a supercritical mantle and hot ice, not oceans
magnetic Field30
No magnetic field - vulnerable to solar radiation
geology40
Extreme volcanic activity may be hazardous
Organic Chemistry80
Core organic elements (CHNO) present
rotation30
Very slow rotation - extreme temperature swings between eternal day and night sides

Physical Properties

Mass
8.30x Earth (4.96e+25 kg)
Radius
2.02x Earth (12,899 km)
This planet: 2.02× Earth radiusEarth: 1× (baseline)
Surface Gravity
2.02x Earth (19.9 m/s²)
Surface Temperature
1,022 K (749 °C / 1,381 °F)
Rotation Period
254.4 hours/day (slower than Earth)
This planet: 254 h/dayEarth: 24 h/day

Orbital Environment

Star Type
G-type (Yellow (Sun-like))
Distance from Star
0.10 AU (14.2 million km)
Orbital Period
11 days

Atmosphere

Hydrogen and helium with water, methane, and ammonia ices

Elemental Composition

H - Hydrogen
36.2%
O - Oxygen
30.5%
Si - Silicon
13.4%

Surface Characteristics

No solid surface - a deep volatile envelope over a supercritical water mantle and hot-ice interior
A binary star system's orrery: two suns close together, a red dashed dead-zone boundary, and a debris trail left by a destroyed world

New: Binary Star Systems 🌀

A system can now orbit two suns. Add a companion star when you build one — close, medium, or wide — and the physics decides what survives: a shared center of mass carves out a dead zone where gravity from both stars tears a world apart, leaving it as debris, and every surviving planet's orbit goes elliptical, moving fastest at closest approach and slowest out at aphelion. Push the separation to wide and the dead zone opens tens of AU across, wide enough to gut a system that would have been stable around one star alone. Stand on a world that made it through and you'll watch two suns cross the sky together.

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