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Entering orbit…
Habitability
36/ 100
Extremely Harsh
HD 283869 b rendered in TerraForge from its measured mass, orbit and star

HD 283869 b

Also written HD 283869b

Sub-NeptuneExtremely Harsh155 light years awayFound 2018
exoplanet.euListed by the Extrasolar Planets Encyclopaedia; not yet in NASA's confirmed catalogue.View on exoplanet.eu

Sub-Neptune, likely · its density could also fit a water world

HD 283869 b, from the Extrasolar Planets Encyclopaedia (found 2018). Measured: 6.52 Earth masses, 0.4 AU, a 4655 K K-type star. Composition inferred from a measured bulk density of 0.87x Earth's, too low for bare rock at this size, suggesting a rocky core under roughly a 1% hydrogen/helium envelope by mass, with an assumed 24-hour day — rotation cannot be measured for exoplanets.

Host star

HD 283869

Type
K-type (Orange)
Temperature
4,655 K
Radius
0.66 ☉
Mass
0.74 ☉
Known planets
1 (this one)
Luminosity
0.184 ☉

Published by the Extrasolar Planets Encyclopaedia. This world’s temperature and habitability score are computed from its star’s published radius and temperature.

Gas Dwarf

Magnetic FieldLow Activity
Why is this a Gas Dwarf?
HD 283869 b has an unusual composition that doesn't fit standard classifications, or lacks the elements needed for complex geological processes.
Barren worlds can form from uncommon element combinations or may be remnants of larger bodies that lost their atmospheres and volatile materials.
Classification Criteria:
Composition doesn't match standard planet typesMass: 6.5x EarthTemperature: 292K

Reading HD 283869 b’s atmosphere

Dominant elements: O, Si, Fe, N, C, HThis is what a telescope would measure while HD 283869 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.HD 283869 b sits about 155 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.The Little Book of ExoplanetsJoshua WinnHow these worlds are found, and what a measurement can honestly tell us.
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Habitability ScoreExtremely Harsh
36
Contributing Factors
temperature100
Optimal temperature range for liquid water and 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
geology60
Some geological activity provides slow nutrient cycling
Organic Chemistry80
Core organic elements (CHNO) present
rotation100
Optimal rotation period - balanced day/night cycle, moderate weather, and good heat distribution

Physical Properties

Mass
6.52x Earth (3.89e+25 kg)
Radius
1.87x Earth (11,902 km)
This planet: 1.87× Earth radiusEarth: 1× (baseline)
Surface Gravity
1.87x Earth (18.3 m/s²)
Surface Temperature
292 K (19 °C / 66 °F)
Rotation Period
24.0 hours/day
This planet: 24 h/dayEarth: 24 h/day

Orbital Environment

Star Type
K-type (Orange)
Distance from Star
0.40 AU (59.8 million km)
Orbital Period
110 days

Atmosphere

Deep hydrogen-helium envelope with photochemical haze

Elemental Composition

O - Oxygen
31.3%
Si - Silicon
25.0%
Fe - Iron
12.5%

Surface Characteristics

No solid surface - a hydrogen-helium envelope wrapped around a rocky core (a sub-Neptune)
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The surface of TOI-700 d as TerraForge draws it: red-leaved trees over green ground under a lavender sky

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