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Entering orbit…
Habitability
11/ 100
Uninhabitable
HIP 54373 c rendered in TerraForge from its measured mass, orbit and star

HIP 54373 c

Also written HIP 54373c

Ice Giant61 light years awayFound 2019
Mass
12.40 × Earth
Radius
3.57 × Earth
Gravity
0.97 g
Surface (est.)
458 K
Year
15.1 days
From Earth
61 ly
Mass
12.40 × Earth
Radius
3.57 × Earth
Gravity
0.97 g
Surface (est.)
458 K
Year
15.1 days
From Earth
61 ly

HIP 54373 system

Type
K-type (Orange)
Spectral type
K5 V
Temperature
4,021 K
Radius
0.565 ☉
Mass
0.57 ☉
Planets
2
Luminosity
0.0599 ☉

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.

HIP 54373 b0.063 AU8.6 M⊕
HIP 54373 c0.099 AUYou are here12 M⊕
Habitable zone

Star and planets drawn to scale: the star is 17 times as wide as HIP 54373 c, so only its edge is in view. Orbits spaced as in the star system view.

Estimated: this planet doesn't transit its star, so its size is inferred, not measured

HIP 54373 c, from the NASA Exoplanet Archive (found 2019). Measured: 12.4 Earth masses, 0.099 AU, a 4021 K K-type star. Composition inferred from a estimated bulk density of 0.27x Earth's, modeled rather than measured since this isn't a transiting planet, larger than even a pure water/ice world of this mass, suggesting a water-rich interior under roughly a 9% hydrogen/helium envelope by mass, with a day locked to its 15.1-day year, as anything orbiting this close would be.

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

Ice Giant
Magnetic FieldExtreme Activity
HIP 54373 c has moderate mass (12.4x 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: 12.4x Earth (5-20x range)✓ Water/Carbon/Nitrogen rich composition

Reading HIP 54373 c’s atmosphere

Dominant elements: H, O, Si, Fe, N, HeThis is what a telescope would measure while HIP 54373 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.HIP 54373 c sits about 61 light-years away, found by the radial velocity 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.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.
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Habitability ScoreUninhabitable
11
Contributing Factors
temperature11
Extremely hot - hostile to known life forms
atmosphere18

Hydrogen and helium with water, methane, and ammonia ices

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 Field100
Magnetic field provides radiation protection
geology40
Extreme volcanic activity may be hazardous
Organic Chemistry80
Core organic elements (CHNO) present
rotation30
Very slow rotation - days and nights each last several Earth days, bringing extreme temperature swings

Physical Properties

Mass
12.40x Earth (7.41e+25 kg)
Radius
2.31x Earth (14,746 km)
This planet: 2.31× Earth radiusEarth: 1× (baseline)
Surface Gravity
2.31x Earth (22.7 m/s²)
Surface Temperature
458 K (184 °C / 364 °F)
Rotation Period
362.4 hours/day (slower than Earth)
This planet: 362 h/dayEarth: 24 h/day

Elemental Composition

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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