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Entering orbit…
Habitability
0/ 100
Uninhabitable
SDSS J1240-0159 b rendered in TerraForge from its measured mass, orbit and star

SDSS J1240-0159 b

Also written SDSS J1240-0159b, SDSS J1240 0159b, SDSS J1240 0159 b

Brown DwarfUninhabitable1288 light years awayFound 2005
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

SDSS J1240-0159 b, from the Extrasolar Planets Encyclopaedia (found 2005). Measured: 4770 Earth masses, 0.00118 AU, a 17000 K B-type star. Composition inferred from a mass of 4770 Earths, which is giant territory whatever its 2.63x density suggests, with a day locked to its 0.0-day year, as anything orbiting this close would be.

Host star

SDSS J1240-0159

Type
B-type (Blue Giant)
Spectral type
DBe
Temperature
17,000 K
Radius
0.01 ☉
Mass
0.31 ☉
Known planets
1 (this one)
Luminosity
7.52e-3 ☉

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

Brown Dwarf

Magnetic FieldNone Activity
Why is this a Brown Dwarf?
SDSS J1240-0159 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: 4770.0x EarthTemperature: 821K

Reading SDSS J1240-0159 b’s atmosphere

Dominant elements: H, He, O, C, NThis is what a telescope would measure while SDSS J1240-0159 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.SDSS J1240-0159 b sits about 1288 light-years away. 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
temperature5
Scorching - hot enough to melt lead, though rock stays solid; no chance for life
atmosphere3
Hydrogen-rich atmosphere typical of gas giants (severely compromised by extreme rotation)
water2
No solid surface — any water is locked in a supercritical mantle and hot ice, not oceans (water stripped by extreme rotation)
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
rotation0
Catastrophic rotation - centrifugal forces would destroy surface structures and prevent atmosphere retention

Physical Properties

Mass
4770.00x Earth (2.85e+28 kg)
Radius
16.83x Earth (107,246 km)
This planet: 16.83× Earth radiusEarth: 1× (baseline)
Surface Gravity
16.83x Earth (165.1 m/s²)
Surface Temperature
821 K (547 °C / 1,017 °F)
Rotation Period
1.0 hours/day (faster than Earth)
This planet: 1 h/dayEarth: 24 h/day

Orbital Environment

Star Type
B-type (Blue Giant)
Distance from Star
0.01 AU (1.5 million km)
Orbital Period
0 days
Time Dilation
Clocks run 7.8 minutes per year slower than deep space — about 10.4 hours over a lifetime

Atmosphere

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

Elemental Composition

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

Surface Characteristics

No surface: a cooling failed star, its methane atmosphere absorbing so much red light it would look magenta to the eye
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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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The surface view's bottom row of buttons on a phone, with an arrow pointing to the VR button beside full screen

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