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Entering orbit…
Habitability
13/ 100
Uninhabitable
Barnard d rendered in TerraForge from its measured mass, orbit and star

Barnard d

Also written Barnardd

Rocky Terrestrial6 light years awayFound 2025
Mass
0.26 × Earth
Radius
0.69 × Earth
Gravity
0.55 g
Surface (est.)
499 K
Year
2.3 days
From Earth
6 ly
Mass
0.26 × Earth
Radius
0.69 × Earth
Gravity
0.55 g
Surface (est.)
499 K
Year
2.3 days
From Earth
6 ly

Barnard's star system

Type
M-type (Red Dwarf)
Spectral type
M3.5-4 V
Temperature
3,195 K
Radius
0.185 ☉
Mass
0.162 ☉
Planets
4
Luminosity
3.55e-3 ☉

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.

Barnard d0.019 AUYou are here0.3 M⊕
Barnard b0.023 AU0.3 M⊕
Barnard c0.027 AU0.3 M⊕
Barnard e0.038 AU0.2 M⊕
Habitable zone

Star and planets drawn to scale: the star is 29 times as wide as Barnard d, 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

Barnard d is the innermost known planet of Barnard's Star, the closest single star to the Sun at about six light-years. It races around the star every 2.34 days at about 0.019 astronomical units, roughly a twentieth of Mercury's distance from the Sun. Its minimum mass is about a quarter of Earth's, 0.263 Earth masses. It is one of four small planets found together around this star, alongside Barnard b, c and e.

Surface. Rocky surface with impact craters, possible volcanic features

Rocky Terrestrial
Life unlikely — too hot for liquid waterNone Activity
Barnard d is dominated by silicate (25.0%) and iron (12.5%) 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: 25.0% + Iron: 12.5% + Magnesium: 3.8%✓ Mass: 0.3x Earth (terrestrial range)

Reading Barnard d’s atmosphere

Dominant elements: O, Si, Fe, N, C, HThis is what a telescope would measure while Barnard d 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.Barnard d sits about 6 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.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.
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
13
Contributing Factors
temperature9
Extremely hot - hostile to known life forms
atmosphere70

Thin CO₂ and nitrogen atmosphere

Nitrogen atmosphere provides protection but not breathable
water26
Limited water content - likely as steam
magnetic Field30
No magnetic field - vulnerable to solar radiation
geology30
Geologically dead - no nutrient recycling
Organic Chemistry80
Core organic elements (CHNO) present
rotation65
Slow rotation - significant day/night temperature variations, but life can adapt

Physical Properties

Mass
0.26x Earth (1.57e+24 kg)
Radius
0.64x Earth (4,082 km)
This planet: 0.64× Earth radiusEarth: 1× (baseline)
Surface Gravity
0.64x Earth (6.3 m/s²)
Surface Temperature
499 K (225 °C / 438 °F)
Rotation Period
56.2 hours/day (slower than Earth)
This planet: 56 h/dayEarth: 24 h/day

Time Dilation

Clocks run 7.5 seconds per year slower than deep space — about 10 minutes over a lifetime

Elemental Composition

How TerraForge built this world

Barnard d, from the NASA Exoplanet Archive (found 2025). Measured: 0.263 Earth masses, 0.0188 AU, a 3195 K M-type star. Composition inferred from an estimated bulk density of 0.79x Earth's, modeled rather than measured since this isn't a transiting planet — the radius is the archive's estimate, so it can't settle how much water there is; read as rock and iron, with a day locked to its 2.3-day year, as anything orbiting this close would be.

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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