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Entering orbit…
Habitability
4/ 100
Uninhabitable
SDSS J1208+3550 b rendered in TerraForge from its measured mass, orbit and star

SDSS J1208+3550 b

Also written SDSS J1208+3550b

Gas Giant678 light years awayFound 2013
Mass
3020.00 × Earth
Radius
12.50 × Earth
Gravity
19.33 g
Surface (est.)
559 K
Year
0.9 hrs
From Earth
678 ly
Mass
3020.00 × Earth
Radius
12.50 × Earth
Gravity
19.33 g
Surface (est.)
559 K
Year
0.9 hrs
From Earth
678 ly

SDSS J1208+3550 system

Type
White dwarf
Spectral type
DA
Temperature
12,000 K
Radius
0.0093 ☉
Mass
0.952 ☉
Planets
1
Luminosity
1.62e-3 ☉

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

SDSS J1208+3550 b0.010 AUYou are here3,020 M⊕
Habitable zone

Star and planets drawn to scale: SDSS J1208+3550 b is 12 times as wide as its star. 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

SDSS J1208+3550 b, from the Extrasolar Planets Encyclopaedia (found 2013). Measured: 3020 Earth masses, 0.00213 AU, a 12000 K B-type star. Composition inferred from a mass of 3020 Earths, which is giant territory whatever its 1.55x density suggests, with a day locked to its 0.0-day year, as anything orbiting this close would be, slowed to 3.82 hours: an assumed spin is not allowed to push a real world past breakup.

Surface. No solid surface - thick gaseous envelope with possible rocky core deep within

Gas Giant
Magnetic FieldExtreme Activity
SDSS J1208+3550 b has 86.0% hydrogen and helium, combined with a mass of 3020.0x Earth, which exceeds the gas giant threshold.
Gas giants form when massive cores capture enormous atmospheres of light gases. They typically form beyond the 'frost line' where volatiles can condense.
Classification Criteria:
✓ Hydrogen + Helium: 86.0% (>60% required)✓ Mass: 3020.0x Earth (>10x required)

Reading SDSS J1208+3550 b’s atmosphere

Dominant elements: H, He, O, C, NThis is what a telescope would measure while SDSS J1208+3550 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 J1208+3550 b sits about 678 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.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.
As an Amazon Associate I earn from qualifying purchases — if you buy through these links, TerraForge may receive a small commission at no extra cost to you.
Habitability ScoreUninhabitable
4
Contributing Factors
temperature7
Extremely hot - hostile to known life forms
atmosphere9

Hydrogen and helium dominated with trace methane and ammonia

Hydrogen-rich atmosphere typical of gas giants (severely compromised by extreme rotation)
water5
No solid surface — any water is locked in a supercritical mantle and hot ice, not oceans (water stripped by extreme rotation)
magnetic Field100
Magnetic field provides radiation protection
geology40
Extreme volcanic activity may be hazardous
Organic Chemistry80
Core organic elements (CHNO) present
rotation5
Extreme rotation (< 4 hrs) - winds exceeding 1000 mph, constant category 5 hurricanes, uninhabitable surface

Physical Properties

Mass
3020.00x Earth (1.80e+28 kg)
Radius
14.45x Earth (92,089 km)
This planet: 14.45× Earth radiusEarth: 1× (baseline)
Surface Gravity
14.45x Earth (141.8 m/s²)
Surface Temperature
559 K (286 °C / 547 °F)
Rotation Period
3.8 hours/day (faster than Earth)
This planet: 4 h/dayEarth: 24 h/day

Time Dilation

Clocks run 7.8 minutes per year slower than deep space — about 10.4 hours 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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