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Entering orbit…
Habitability
0/ 100
Uninhabitable
HIP 73990 Ac rendered in TerraForge from its measured mass, orbit and star

HIP 73990 Ac

Brown Dwarf408 light years awayFound 2015
Mass
6990.00 × Earth
Radius
12.00 × Earth
Gravity
48.54 g
Surface (est.)
1,185 K
Year (est.)
159 years
From Earth
408 ly
Mass
6990.00 × Earth
Radius
12.00 × Earth
Gravity
48.54 g
Surface (est.)
1,185 K
Year (est.)
159 years
From Earth
408 ly

HIP 73990 A system

Type
F-type (White)
Spectral type
A9V
Temperature
7,450 K
Mass
1.72 ☉
Planets
2

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.

HIP 73990 Ab20.00 AU6,670 M⊕
HIP 73990 Ac32.00 AUYou are here6,990 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

HIP 73990 Ac, from the Extrasolar Planets Encyclopaedia (found 2015). Measured: 6990 Earth masses, 32 AU, a 7450 K F-type star. Composition inferred from a mass of 6990 Earths, which is giant territory whatever its 4.05x 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
HIP 73990 Ac 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: 6990.0x EarthTemperature: 1185K

Reading HIP 73990 Ac’s atmosphere

Dominant elements: H, He, O, C, NThis is what a telescope would measure while HIP 73990 Ac 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.HIP 73990 Ac sits about 408 light-years away, found by the imaging 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
temperature0
Inferno world - temperatures exceed all possibility of 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
6990.00x Earth (4.17e+28 kg)
Radius
19.12x Earth (121,815 km)
This planet: 19.12× Earth radiusEarth: 1× (baseline)
Surface Gravity
19.12x Earth (187.6 m/s²)
Surface Temperature
1,185 K (912 °C / 1,673 °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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