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Entering orbit…
Habitability
0/ 100
Uninhabitable
HD 50554 d rendered in TerraForge from its measured mass, orbit and star

HD 50554 d

Also written HD 50554d

Rocky Terrestrial102 light years awayFound 2026
Mass
10.40 × Earth
Radius
1.41 × Earth
Gravity
5.23 g
Surface (est.)
719 K
Year
28.1 days
From Earth
102 ly
Mass
10.40 × Earth
Radius
1.41 × Earth
Gravity
5.23 g
Surface (est.)
719 K
Year
28.1 days
From Earth
102 ly

HD 50554 system

Type
G-type (Yellow (Sun-like))
Spectral type
F8 V
Temperature
5,968 K
Radius
1.15 ☉
Mass
1.04 ☉
Planets
3
Luminosity
1.50 ☉

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.

HD 50554 c0.065 AU5.3 M⊕
HD 50554 d0.18 AUYou are here10 M⊕
HD 50554 b2.34 AU1,860 M⊕
Habitable zone

Star and planets drawn to scale: the star is 89 times as wide as HD 50554 d, so only its edge is in view. Orbits spaced as in the star system view.

HD 50554 d is the outer of two small planets found in 2026 crossing in front of HD 50554, an F-type star about 100 light-years away that also hosts a giant planet on a wide orbit. HD 50554 d orbits every 28.1 days and is about 1.4 times Earth's width, a little larger than its inner sibling, HD 50554 c.

Surface. Rocky surface with impact craters, possible volcanic features

Rocky Terrestrial
Magnetic FieldExtreme Activity
HD 50554 d is dominated by silicate (36.6%) and iron (24.4%) content, forming a rocky terrestrial body.
Rocky terrestrial planets are primarily composed of silicate rocks and metals. They're the most common type of small planet in the universe.
Classification Criteria:
✓ Silicon: 36.6% + Iron: 24.4% + Magnesium: 12.2%✓ Mass: 10.4x Earth (terrestrial range)

Reading HD 50554 d’s atmosphere

Dominant elements: Si, Fe, Mg, Ni, S, AlThis is what a telescope would measure while HD 50554 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.HD 50554 d sits about 102 light-years away, found by the transit 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
temperature4
Scorching - hot enough to melt lead, though rock stays solid; no chance for life
atmosphere10

Minimal or none

No atmosphere - exposed to radiation and temperature extremes
water0
No water - the recipe has no hydrogen and oxygen to form it
magnetic Field100
Magnetic field provides radiation protection
geology40
Extreme volcanic activity may be hazardous
Organic Chemistry20
Limited organic chemistry potential
rotation100
Optimal rotation period - balanced day/night cycle, moderate weather, and good heat distribution

Physical Properties

Mass
10.40x Earth (6.21e+25 kg)
Radius
2.18x Earth (13,907 km)
This planet: 2.18× Earth radiusEarth: 1× (baseline)
Surface Gravity
2.18x Earth (21.4 m/s²)
Surface Temperature
719 K (446 °C / 835 °F)
Rotation Period
24.0 hours/day
This planet: 24 h/dayEarth: 24 h/day

Elemental Composition

How TerraForge built this world

HD 50554 d, from the NASA Exoplanet Archive (found 2026). Measured: 10.4 Earth masses, 0.183 AU, a 5968 K G-type star. Composition inferred from a measured bulk density of 3.71x Earth's, far too high for silicates alone — an iron-rich world, with an assumed 24-hour day — rotation cannot be measured for exoplanets.

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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