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Entering orbit…
Habitability
9/ 100
Uninhabitable

Reading TOI-5120 b’s atmosphere

Dominant elements: H, He, O, C, NThis is what a telescope would measure while TOI-5120 b 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-5120 b sits about 750 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.
TOI-5120 b rendered in TerraForge from its measured mass, orbit and star

TOI-5120 b

Also written TOI-5120b, TOI 5120b, TOI 5120 b

Gas GiantUninhabitable750 light years awayFound 2026

TOI-5120 b is close to a twin of Jupiter in size and mass, about 1.23 times Jupiter's mass and 0.97 times its width, but it circles its star every 24.9 days at 0.17 astronomical units (one astronomical unit is the Earth–Sun distance). NASA's TESS satellite flagged it as a candidate from a regular dip in the starlight, called a transit, as the planet crossed in front of its star. A team led by E. Knudstrup confirmed it in 2026 by measuring the star's slight wobble with two spectrographs, the Tull coudé spectrograph at McDonald Observatory and FIES on the Nordic Optical Telescope, monitoring it from 2022 to 2025. Combining the two methods gives both the planet's size and its mass.

Read the full article

Host star

TOI-5120

Type
G-type (Yellow (Sun-like))
Temperature
5,763 K
Radius
1.42 ☉
Mass
1.12 ☉
Known planets
1 (this one)
Luminosity
2.17 ☉

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.

Gas Giant

Magnetic FieldExtreme Activity
Why is this a Gas Giant?TOI-5120 b has 86.0% hydrogen and helium, combined with a mass of 391.0x Earth, which exceeds the gas giant threshold.
Gas giants form when massive cores capture enormous atmospheres of light gases. They typically form beyond the 'frost line' where volatiles can condense.
Classification Criteria:
✓ Hydrogen + Helium: 86.0% (>60% required)✓ Mass: 391.0x Earth (>10x required)
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.
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
9
Contributing Factors
temperature5
Scorching - hot enough to melt lead, though rock stays solid; no chance for 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
geology40
Extreme volcanic activity may be hazardous
Organic Chemistry80
Core organic elements (CHNO) present
rotation100
Optimal rotation period - balanced day/night cycle, moderate weather, and good heat distribution

Physical Properties

Mass
391.00x Earth (2.34e+27 kg)
Radius
7.31x Earth (46,587 km)
This planet: 7.31× Earth radiusEarth: 1× (baseline)
Surface Gravity
7.31x Earth (71.7 m/s²)
Surface Temperature
816 K (542 °C / 1,008 °F)
Rotation Period
24.0 hours/day
This planet: 24 h/dayEarth: 24 h/day

Orbital Environment

Star Type
G-type (Yellow (Sun-like))
Distance from Star
0.17 AU (25.7 million km)
Orbital Period
26 days

Atmosphere

Hydrogen and helium dominated with trace methane and ammonia

Elemental Composition

H - Hydrogen
53.8%
He - Helium
32.3%
O - Oxygen
5.4%

Surface Characteristics

No solid surface - thick gaseous envelope with possible rocky core deep within

How TerraForge built this world

TOI-5120 b, from the NASA Exoplanet Archive (found 2026). Measured: 391 Earth masses, 0.172 AU, a 5763 K G-type star. Composition inferred from a mass of 391 Earths, which is giant territory whatever its 0.30x density suggests, with an assumed 24-hour day — rotation cannot be measured for exoplanets.

A banded gas giant with four moons in different colors: a yellow sulfur moon, two rust-red rock moons and a blue water moon

New: Choose What Your Moons Are Made Of 🌙

Every moon used to be grey rock, white ice or blue ocean, decided for you. Now each one has a "Made of" choice in the builder's Moons tab — silicate rock, iron, water ice, carbon, sulfur, or nitrogen and methane ice — and the physics decides what that becomes. Put water ice too close to the star and it boils off to bare rock. Put sulfur where a neighbouring moon keeps it tidally flexed and it erupts in Io's yellows. Give a Titan-sized moon nitrogen ice far from the sun and it wraps itself in haze. Hang a water moon about the mass of Earth off a giant planet in the habitable zone and it can hold air and open seas — scored for life on the same scale as a planet, with a day as long as its orbit. A tint slider nudges the colour, but only as far as that material could really go.

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We only keep your email and the username you choose. We never share or sell your email, and we don't send marketing — we use it only to email you a sign-in code. Read our privacy policy.

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