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Entering orbit…
Habitability
5/ 100
Uninhabitable

HD 191939 b

Ice GiantUninhabitable175 light years awayFound 2020

HD 191939 b, from the NASA Exoplanet Archive (found 2020). Measured: 10 Earth masses, 0.0804 AU, a 5348 K G-type star. Composition inferred from a measured bulk density of 0.25x Earth's — too light for bare rock, so a large fraction of water and ice, with a day locked to its 8.9-day year, as anything orbiting this close would be.

Host star

HD 191939

Type
G-type (Yellow (Sun-like))
Spectral type
G9 V
Temperature
5,348 K
Radius
0.94 ☉
Mass
0.81 ☉
Known planets
6, including this one
Luminosity
0.650 ☉

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

Extreme Activity
Why is this a Ice Giant?Your planet has moderate mass (10.0x 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: 10.0x 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.
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Habitability ScoreUninhabitable
5
Contributing Factors
temperature5
Scorching - hot enough to melt lead, though rock stays solid; no chance for 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
10.00x Earth (5.97e+25 kg)
Radius
2.15x Earth (13,726 km)
This planet: 2.15× Earth radiusEarth: 1× (baseline)
Surface Gravity
2.15x Earth (21.1 m/s²)
Surface Temperature
947 K (674 °C / 1,246 °F)
Rotation Period
213.1 hours/day (slower than Earth)
This planet: 213 h/dayEarth: 24 h/day

Orbital Environment

Star Type
G-type (Yellow (Sun-like))
Distance from Star
0.08 AU (12 million km)
Orbital Period
8 days
Time Dilation
Clocks run 5.8 seconds per year slower than deep space — about 8 minutes over a lifetime

Atmosphere

Hydrogen and helium with water, methane, and ammonia ices

Elemental Composition

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

Surface Characteristics

No solid surface - a deep volatile envelope over a supercritical water mantle and hot-ice interior
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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