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Entering orbit…
Habitability
0/ 100
Uninhabitable
HD 39392 b rendered in TerraForge from its measured mass, orbit and star

HD 39392 b

Also written HD 39392b

Brown Dwarf307 light years awayFound 2016
Mass
5500.00 × Earth
Radius
12.10 × Earth
Gravity
37.57 g
Surface (est.)
682 K
Year
394 days
From Earth
307 ly
Mass
5500.00 × Earth
Radius
12.10 × Earth
Gravity
37.57 g
Surface (est.)
682 K
Year
394 days
From Earth
307 ly

HD 39392 system

Type
G-type (Yellow (Sun-like))
Spectral type
F8
Temperature
5,951 K
Mass
1.08 ☉
Planets
1

Published by the Extrasolar Planets Encyclopaedia. This star’s luminosity has not been published, so this world’s temperature and habitability score fall back to a typical G-type star.

HD 39392 b1.08 AUYou are here5,500 M⊕
Habitable zone

Planets drawn to scale with each other; the star's size is not measured. Orbits spaced as in the star system view.

exoplanet.euListed by the Extrasolar Planets Encyclopaedia; not yet in NASA's confirmed catalogue.View on exoplanet.eu

Estimated: this planet doesn't transit its star, so its size is inferred, not measured

HD 39392 b, from the Extrasolar Planets Encyclopaedia (found 2016). Measured: 5500 Earth masses, 1.08 AU, a 5951 K G-type star. Composition inferred from a mass of 5500 Earths, which is giant territory whatever its 3.10x density suggests, with an assumed 24-hour day — rotation cannot be measured for exoplanets.

Surface. No surface: a cooling failed star, its methane atmosphere absorbing so much red light it would look magenta to the eye

Brown Dwarf
Magnetic FieldNone Activity
HD 39392 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: 5500.0x EarthTemperature: 682K

Reading HD 39392 b’s atmosphere

Dominant elements: H, He, O, C, NThis is what a telescope would measure while HD 39392 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 39392 b sits about 307 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.
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Habitability ScoreUninhabitable
0
Contributing Factors
temperature4
Scorching - hot enough to melt lead, though rock stays solid; no chance for life
atmosphere30

Hydrogen and helium dominated by methane absorption, with water clouds below

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 Field20
A strong field, but no surface beneath it — there is nothing here for it to shelter
geology30
Geologically dead - no nutrient recycling
Organic Chemistry80
Core organic elements (CHNO) present
rotation100
Optimal rotation period - balanced day/night cycle, moderate weather, and good heat distribution

Physical Properties

Mass
5500.00x Earth (3.28e+28 kg)
Radius
17.65x Earth (112,459 km)
This planet: 17.65× Earth radiusEarth: 1× (baseline)
Surface Gravity
17.65x Earth (173.2 m/s²)
Surface Temperature
682 K (409 °C / 769 °F)
Rotation Period
24.0 hours/day
This planet: 24 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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