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Entering orbit…
Habitability
0/ 100
Uninhabitable
TOI-5143 Ab rendered in TerraForge from its measured mass, orbit and star

TOI-5143 Ab

Also written TOI 5143 Ab

Sub-NeptuneUninhabitable584 light years awayFound 2025
exoplanet.euListed by the Extrasolar Planets Encyclopaedia; not yet in NASA's confirmed catalogue.View on exoplanet.eu

TOI-5143 Ab, from the Extrasolar Planets Encyclopaedia (found 2025). Measured: 8.39 Earth masses, 0.0336 AU, a 5183 K K-type star. Composition inferred from a measured bulk density of 0.35x Earth's, too low for bare rock at this size, suggesting a rocky core under roughly a 7% hydrogen/helium envelope by mass, with a day locked to its 2.4-day year, as anything orbiting this close would be.

Host star

TOI-5143

Type
K-type (Orange)
Spectral type
G9/K0V
Temperature
5,183 K
Radius
0.852 ☉
Mass
0.864 ☉
Known planets
2, including this one
Luminosity
0.472 ☉

Published by the Extrasolar Planets Encyclopaedia. This world’s temperature and habitability score are computed from its star’s published radius and temperature.

Gas Dwarf

Life unlikely — too hot for liquid waterMagnetic FieldLow Activity
Why is this a Gas Dwarf?
TOI-5143 Ab has an unusual composition that doesn't fit standard classifications, or lacks the elements needed for complex geological processes.
Barren worlds can form from uncommon element combinations or may be remnants of larger bodies that lost their atmospheres and volatile materials.
Classification Criteria:
Composition doesn't match standard planet typesMass: 8.4x EarthTemperature: 1272K

Reading TOI-5143 Ab’s atmosphere

Dominant elements: O, Si, Fe, N, C, HThis is what a telescope would measure while TOI-5143 Ab 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.TOI-5143 Ab sits about 584 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.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
0
Contributing Factors
temperature0
Inferno world - temperatures exceed all possibility of life
atmosphere30
Hydrogen-rich atmosphere typical of gas giants
water15
No solid surface — any water is locked in a supercritical mantle and hot ice, not oceans
magnetic Field100
Magnetic field provides radiation protection
geology60
Some geological activity provides slow nutrient cycling
Organic Chemistry80
Core organic elements (CHNO) present
rotation65
Slow rotation - significant day/night temperature variations, but life can adapt

Physical Properties

Mass
8.39x Earth (5.01e+25 kg)
Radius
2.03x Earth (12,946 km)
This planet: 2.03× Earth radiusEarth: 1× (baseline)
Surface Gravity
2.03x Earth (19.9 m/s²)
Surface Temperature
1,272 K (999 °C / 1,830 °F)
Rotation Period
57.1 hours/day (slower than Earth)
This planet: 57 h/dayEarth: 24 h/day

Orbital Environment

Star Type
K-type (Orange)
Distance from Star
0.03 AU (5.03 million km)
Orbital Period
3 days
Time Dilation
Clocks run 9.7 seconds per year slower than deep space — about 13 minutes over a lifetime

Atmosphere

Deep hydrogen-helium envelope with photochemical haze

Elemental Composition

O - Oxygen
31.3%
Si - Silicon
25.0%
Fe - Iron
12.5%

Surface Characteristics

No solid surface - a hydrogen-helium envelope wrapped around a rocky core (a sub-Neptune)
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The surface of TOI-700 d as TerraForge draws it: red-leaved trees over green ground under a lavender sky

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