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Entering orbit…
Habitability
0/ 100
Uninhabitable
HD 106906 (AB)c rendered in TerraForge from its measured mass, orbit and star

HD 106906 (AB)c

Brown DwarfUninhabitable300 light years awayFound 2026
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 106906 (AB)c, from the Extrasolar Planets Encyclopaedia (found 2026). Measured: 4290 Earth masses, 6.5 AU, a 6798 K F-type star. Composition inferred from a mass of 4290 Earths, which is giant territory whatever its 2.31x density suggests, with an assumed 24-hour day — rotation cannot be measured for exoplanets.

Host star

HD 106906

Type
F-type (White)
Spectral type
F5V+F5V
Temperature
6,798 K
Mass
1.5 ☉
Known planets
2, including this one

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 F-type star.

Brown Dwarf

Magnetic FieldNone Activity
Why is this a Brown Dwarf?
HD 106906 (AB)c 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: 4290.0x EarthTemperature: 372K

Reading HD 106906 (AB)c’s atmosphere

Dominant elements: H, He, O, C, NThis is what a telescope would measure while HD 106906 (AB)c 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 106906 (AB)c sits about 300 light-years away, found by the astrometry 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
temperature40
Extreme temperature - very difficult for 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 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
4290.00x Earth (2.56e+28 kg)
Radius
16.25x Earth (103,521 km)
This planet: 16.25× Earth radiusEarth: 1× (baseline)
Surface Gravity
16.25x Earth (159.4 m/s²)
Surface Temperature
372 K (99 °C / 211 °F)
Rotation Period
24.0 hours/day
This planet: 24 h/dayEarth: 24 h/day

Orbital Environment

Star Type
F-type (White)
Distance from Star
6.50 AU (972 million km)
Orbital Period
14.5 years

Atmosphere

Cold hydrogen and helium with ammonia and water clouds

Elemental Composition

H - Hydrogen
53.8%
He - Helium
32.3%
O - Oxygen
5.4%

Surface Characteristics

No surface: the coldest class of failed star, barely warmer than a summer day and glowing only in the infrared
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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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Open any planet's surface view on your phone and look around just by moving it: hold it up, turn on the spot, and the view turns with you. In Chrome on Android you also get a VR button, in the row along the bottom:

The surface view's bottom row of buttons on a phone, with an arrow pointing to the VR button beside full screen

Tap it, drop your phone into a headset viewer, and you're standing on the ground under a star that isn't ours. It only appears where your browser can do VR.

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