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Entering orbit…
Habitability
0/ 100
Uninhabitable
MARVELS-18 b rendered in TerraForge from its measured mass, orbit and star

MARVELS-18 b

Also written MARVELS-18b, MARVELS 18b, MARVELS 18 b

Brown DwarfUninhabitable1418 light years awayFound 2017
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

MARVELS-18 b, from the Extrasolar Planets Encyclopaedia (found 2017). Measured: 7760 Earth masses, 0.51 AU, a 6295 K F-type star. Composition inferred from a mass of 7760 Earths, which is giant territory whatever its 4.49x density suggests, with an assumed 24-hour day — rotation cannot be measured for exoplanets.

Host star

TYC 3556-3602-1

Type
F-type (White)
Temperature
6,295 K
Radius
1.23 ☉
Mass
1.25 ☉
Known planets
1 (this one)
Luminosity
2.14 ☉

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?
MARVELS-18 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: 7760.0x EarthTemperature: 1475K

Reading MARVELS-18 b’s atmosphere

Dominant elements: H, He, O, C, NThis is what a telescope would measure while MARVELS-18 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.MARVELS-18 b sits about 1419 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
temperature0
Inferno world - temperatures exceed all possibility of life
atmosphere30
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
7760.00x Earth (4.63e+28 kg)
Radius
19.80x Earth (126,133 km)
This planet: 19.80× Earth radiusEarth: 1× (baseline)
Surface Gravity
19.80x Earth (194.2 m/s²)
Surface Temperature
1,475 K (1,202 °C / 2,195 °F)
Rotation Period
24.0 hours/day
This planet: 24 h/dayEarth: 24 h/day

Orbital Environment

Star Type
F-type (White)
Distance from Star
0.51 AU (76.3 million km)
Orbital Period
117 days

Atmosphere

Hydrogen and helium with iron and silicate cloud decks - hot enough to rain molten metal

Elemental Composition

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

Surface Characteristics

No surface: a deuterium-burning sphere the size of Jupiter and dozens of times its mass, glowing dull red from its own heat
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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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