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Entering orbit…
Habitability
0/ 100
Uninhabitable
NN Ser d rendered in TerraForge from its measured mass, orbit and star

NN Ser d

Also written NN Serd

Gas Giant1682 light years awayFound 2010
Mass
725.00 × Earth
Radius
13.30 × Earth
Gravity
4.10 g
Surface (est.)
2,685 K
Year
7.9 years
From Earth
1,683 ly
Mass
725.00 × Earth
Radius
13.30 × Earth
Gravity
4.10 g
Surface (est.)
2,685 K
Year
7.9 years
From Earth
1,683 ly

NN Ser system

Type
White dwarf
Spectral type
WD
Temperature
57,000 K
Mass
0.535 ☉
Planets
2

Published by the NASA Exoplanet Archive. This star’s luminosity has not been published, so this world’s temperature and habitability score fall back to a typical O-type star.

NN Ser d3.39 AUYou are here725 M⊕
NN Ser c5.35 AU2,330 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.

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

NN Ser d, from the NASA Exoplanet Archive (found 2010). Measured: 725 Earth masses, 3.39 AU, a 57000 K O-type star. Composition inferred from a mass of 725 Earths, which is giant territory whatever its 0.31x density suggests, with an assumed 24-hour day — rotation cannot be measured for exoplanets.

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

Gas Giant
Magnetic FieldExtreme Activity
NN Ser d has 86.0% hydrogen and helium, combined with a mass of 725.0x 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: 725.0x Earth (>10x required)

Reading NN Ser d’s atmosphere

Dominant elements: H, He, O, C, NThis is what a telescope would measure while NN Ser d 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.NN Ser d sits about 1683 light-years away, found by the eclipse timing variations 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 ScoreUninhabitable
0
Contributing Factors
temperature0
Inferno world - temperatures exceed all possibility of life
atmosphere30

Hydrogen and helium dominated with trace methane and ammonia

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
geology40
Extreme volcanic activity may be hazardous
Organic Chemistry80
Core organic elements (CHNO) present
rotation100
Optimal rotation period - balanced day/night cycle, moderate weather, and good heat distribution

Physical Properties

Mass
725.00x Earth (4.33e+27 kg)
Radius
8.98x Earth (57,234 km)
This planet: 8.98× Earth radiusEarth: 1× (baseline)
Surface Gravity
8.98x Earth (88.1 m/s²)
Surface Temperature
2,685 K (2,412 °C / 4,373 °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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