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Entering orbit…
Habitability
0/ 100
Uninhabitable
GJ 9827 b rendered in TerraForge from its measured mass, orbit and star

GJ 9827 b

Also written GJ 9827b

Lava World97 light years awayFound 2017
Mass
4.28 × Earth
Radius
1.44 × Earth
Gravity
2.06 g
Surface (est.)
1,149 K
Year
29.0 hrs
From Earth
96.9 ly
Mass
4.28 × Earth
Radius
1.44 × Earth
Gravity
2.06 g
Surface (est.)
1,149 K
Year
29.0 hrs
From Earth
96.9 ly

GJ 9827 system

Type
K-type (Orange)
Spectral type
K7 V
Temperature
4,236 K
Radius
0.58 ☉
Mass
0.62 ☉
Planets
3
Luminosity
0.0990 ☉

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.

GJ 9827 b0.019 AUYou are here4.3 M⊕
GJ 9827 c0.040 AU1.9 M⊕
GJ 9827 d0.053 AU3.0 M⊕
Habitable zone

Star and planets drawn to scale: the star is 44 times as wide as GJ 9827 b, so only its edge is in view. Orbits spaced as in the star system view.

GJ 9827 b, from the NASA Exoplanet Archive (found 2017). Measured: 4.28 Earth masses, 0.0189 AU, a 4236 K K-type star. Composition inferred from a measured bulk density of 1.43x Earth's, which is rock and iron, with a day locked to its 1.2-day year, as anything orbiting this close would be.

Surface. Molten surface with lava flows, volcanic activity everywhere

Lava World
Life unlikely — too hot for liquid waterMagnetic FieldExtreme Activity
GJ 9827 b's proximity to its star (0.02 AU) results in extreme surface temperatures of 1149K.
Lava worlds orbit so close to their stars that rocky surfaces melt into oceans of molten rock. Recent planet formation can also create temporary lava worlds.
Classification Criteria:
✓ Temperature: 1149K (>1000K)

Reading GJ 9827 b’s atmosphere

Dominant elements: O, Si, Fe, N, C, HThis is what a telescope would measure while GJ 9827 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.GJ 9827 b sits about 97 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.Imagined LifeJames Trefil & Michael SummersWhat could live on a world like this one: ice shells, supergravity, tidally locked twilight.
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Habitability ScoreUninhabitable
0
Contributing Factors
temperature0
Inferno world - temperatures exceed all possibility of life
atmosphere40

Vaporized rock and metals

Atmosphere present but composition not ideal for life
water8
Limited water content - boiling away, little would be retained
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
4.28x Earth (2.56e+25 kg)
Radius
1.62x Earth (10,344 km)
This planet: 1.62× Earth radiusEarth: 1× (baseline)
Surface Gravity
1.62x Earth (15.9 m/s²)
Surface Temperature
1,149 K (876 °C / 1,609 °F)
Rotation Period
29.0 hours/day (slower than Earth)
This planet: 29 h/dayEarth: 24 h/day

Time Dilation

Clocks run 17.3 seconds per year slower than deep space — about 23 minutes over a lifetime

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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