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Entering orbit…
Habitability
15/ 100
Uninhabitable
LHS 1678 d rendered in TerraForge from its measured mass, orbit and star

LHS 1678 d

Also written LHS 1678d

Rocky Terrestrial65 light years awayFound 2024
Mass
0.91 × Earth
Radius
0.98 × Earth
Gravity
0.94 g
Surface (est.)
490 K
Year
5.0 days
From Earth
64.9 ly
Mass
0.91 × Earth
Radius
0.98 × Earth
Gravity
0.94 g
Surface (est.)
490 K
Year
5.0 days
From Earth
64.9 ly

LHS 1678 system

Type
M-type (Red Dwarf)
Spectral type
M2.0 V
Temperature
3,490 K
Radius
0.329 ☉
Mass
0.345 ☉
Planets
3
Luminosity
0.0145 ☉

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.

LHS 1678 b0.012 AU0.3 M⊕
LHS 1678 c0.033 AU1.4 M⊕
LHS 1678 d0.040 AUYou are here0.9 M⊕
Habitable zone

Star and planets drawn to scale: the star is 37 times as wide as LHS 1678 d, so only its edge is in view. Orbits spaced as in the star system view.

LHS 1678 d, from the NASA Exoplanet Archive (found 2024). Measured: 0.907 Earth masses, 0.04 AU, a 3490 K M-type star. Composition inferred from a measured bulk density of 0.96x Earth's, which is rock and iron, with a day locked to its 5.0-day year, as anything orbiting this close would be.

Surface. Rocky surface with impact craters, possible volcanic features

Rocky Terrestrial
Life unlikely — too hot for liquid waterModerate Activity
LHS 1678 d is dominated by silicate (24.6%) and iron (12.3%) 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: 24.6% + Iron: 12.3% + Magnesium: 3.7%✓ Mass: 0.9x Earth (terrestrial range)

Reading LHS 1678 d’s atmosphere

Dominant elements: O, Si, Fe, N, H, CThis is what a telescope would measure while LHS 1678 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.LHS 1678 d sits about 65 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.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
15
Contributing Factors
temperature10
Extremely hot - hostile to known life forms
atmosphere70

Thin CO₂ and nitrogen atmosphere

Nitrogen atmosphere provides protection but not breathable
water28
Limited water content - likely as steam
magnetic Field30
No magnetic field - vulnerable to solar radiation
geology90
Active geology recycles nutrients and drives carbon cycle
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
0.91x Earth (5.42e+24 kg)
Radius
0.97x Earth (6,167 km)
This planet: 0.97× Earth radiusEarth: 1× (baseline)
Surface Gravity
0.97x Earth (9.5 m/s²)
Surface Temperature
490 K (217 °C / 423 °F)
Rotation Period
119.3 hours/day (slower than Earth)
This planet: 119 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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