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Entering orbit…
Habitability
0/ 100
Uninhabitable
11 UMi b rendered in TerraForge from its measured mass, orbit and star

11 UMi b

Also written 11 UMib

Brown Dwarf408 light years awayFound 2009
Mass
4680.00 × Earth
Radius
12.30 × Earth
Gravity
30.93 g
Surface (est.)
912 K
Year
516 days
From Earth
408 ly
Mass
4680.00 × Earth
Radius
12.30 × Earth
Gravity
30.93 g
Surface (est.)
912 K
Year
516 days
From Earth
408 ly

11 UMi system

Type
K-type (Orange)
Spectral type
K4 III
Temperature
4,213 K
Radius
29.8 ☉
Mass
2.78 ☉
Planets
1
Luminosity
269 ☉

Published by the NASA Exoplanet Archive. This world’s temperature and habitability score are computed from this star’s measured luminosity, not from a stand-in for its class.

11 UMi b1.53 AUYou are here4,680 M⊕
Habitable zone

Star and planets drawn to scale: the star is 265 times as wide as 11 UMi b, so only its edge is in view. Orbits spaced as in the star system view.

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

11 UMi b, from the NASA Exoplanet Archive (found 2009). Measured: 4680 Earth masses, 1.53 AU, a 4213 K K-type star. Composition inferred from a mass of 4680 Earths, which is giant territory whatever its 2.51x 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
11 UMi 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: 4680.0x EarthTemperature: 912K

Reading 11 UMi b’s atmosphere

Dominant elements: H, He, O, C, NThis is what a telescope would measure while 11 UMi 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.11 UMi b sits about 408 light-years away, found by the radial velocity 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
temperature1
Scorching - hot enough to melt lead, though rock stays solid; no chance for 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
4680.00x Earth (2.79e+28 kg)
Radius
16.73x Earth (106,567 km)
This planet: 16.73× Earth radiusEarth: 1× (baseline)
Surface Gravity
16.73x Earth (164.1 m/s²)
Surface Temperature
912 K (639 °C / 1,183 °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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