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Entering orbit…
Habitability
0/ 100
Uninhabitable

Reading TOI-789 b’s atmosphere

Dominant elements: Si, Fe, Mg, Ni, S, AlThis is what a telescope would measure while TOI-789 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-789 b sits about 142 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-789 b

Also written TOI-789b, TOI 789b, TOI 789 b

Rocky TerrestrialUninhabitable141 light years awayFound 2026

TOI-789 b, from the NASA Exoplanet Archive (found 2026). Measured: 3.7 Earth masses, 0.043 AU, a 3471 K M-type star. Composition inferred from a measured bulk density of 2.25x Earth's, far too high for silicates alone — an iron-rich world, with a day locked to its 5.5-day year, as anything orbiting this close would be.

Host star

TOI-789

Type
M-type (Red Dwarf)
Spectral type
M3 V
Temperature
3,471 K
Radius
0.371 ☉
Mass
0.358 ☉
Known planets
3, including this one
Luminosity
0.0178 ☉

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.

Rocky Terrestrial

High Activity
Why is this a Rocky Terrestrial?TOI-789 b is dominated by silicate (36.6%) and iron (24.4%) content, forming a rocky terrestrial body.
Rocky terrestrial planets are primarily composed of silicate rocks and metals. They're the most common type of small planet in the universe.
Classification Criteria:
✓ Silicon: 36.6% + Iron: 24.4% + Magnesium: 12.2%✓ Mass: 3.7x Earth (terrestrial range)
Further reading
The Little Book of ExoplanetsJoshua WinnHow these worlds are found, and what a measurement can honestly tell us.Exoplanets: Diamond Worlds, Super Earths, Pulsar PlanetsMichael Summers & James TrefilThe strange end of the catalogue — carbon worlds, molten rock, planets orbiting dead stars.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
temperature15
Extremely hot - hostile to known life forms
atmosphere10
No atmosphere - exposed to radiation and temperature extremes
water0
No water - the recipe has no hydrogen and oxygen to form it
magnetic Field30
No magnetic field - vulnerable to solar radiation
geology90
Active geology recycles nutrients and drives carbon cycle
Organic Chemistry20
Limited organic chemistry potential
rotation30
Very slow rotation - extreme temperature swings between eternal day and night sides

Physical Properties

Mass
3.70x Earth (2.21e+25 kg)
Radius
1.55x Earth (9,854 km)
This planet: 1.55× Earth radiusEarth: 1× (baseline)
Surface Gravity
1.55x Earth (15.2 m/s²)
Surface Temperature
490 K (217 °C / 422 °F)
Rotation Period
130.8 hours/day (slower than Earth)
This planet: 131 h/dayEarth: 24 h/day

Orbital Environment

Star Type
M-type (Red Dwarf)
Distance from Star
0.04 AU (6.43 million km)
Orbital Period
6 days

Atmosphere

Minimal or none

Elemental Composition

Si - Silicon
36.6%
Fe - Iron
24.4%
Mg - Magnesium
12.2%

Surface Characteristics

Rocky surface with impact craters, possible volcanic features
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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