Create your free account

Enter your email and we'll send a 6-digit code — no password needed.
We only keep your email and the username you choose. We never share or sell your email, and we don't send marketing — we use it only to email you a sign-in code. Read our privacy policy.
Entering orbit…
Habitability
34/ 100
Extremely Harsh

Reading HD 69830 d’s atmosphere

Dominant elements: H, O, He, Si, Fe, NThis is what a telescope would measure while HD 69830 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 69830 d sits about 41 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.

HD 69830 d

Gas GiantExtremely Harsh41 light years awayFound 2006

HD 69830 d, from the NASA Exoplanet Archive (found 2006). Measured: 18.1 Earth masses, 0.63 AU, a 5385 K G-type star. Composition inferred from a estimated bulk density of 0.21x Earth's, modeled rather than measured since this isn't a transiting planet, larger than even a pure water/ice world of this mass, suggesting a water-rich interior under roughly a 22% hydrogen/helium envelope by mass, with an assumed 24-hour day — rotation cannot be measured for exoplanets.

Host star

HD 69830

Type
G-type (Yellow (Sun-like))
Spectral type
K0V
Temperature
5,385 K
Radius
0.887 ☉
Mass
0.86 ☉
Known planets
3, including this one
Luminosity
0.603 ☉

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.

Gas Giant

No life — no phosphorus — DNA and ATP are built on itMagnetic FieldExtreme Activity
Why is this a Gas Giant?Your planet has 61.4% hydrogen and helium, combined with a mass of 18.1x 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: 61.4% (>60% required)✓ Mass: 18.1x Earth (>10x required)
Further reading
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.Envisioning ExoplanetsMichael CarrollWhat these worlds might look like from the ground, painted from the same measurements this page renders.Imagined LifeJames Trefil & Michael SummersWhat could live on a world like this one: ice shells, supergravity, tidally locked twilight.
As an Amazon Associate I earn from qualifying purchases — if you buy through these links, TerraForge may receive a small commission at no extra cost to you.
Habitability ScoreExtremely Harsh
34
Contributing Factors
temperature70
Challenging but potentially habitable temperature
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 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
18.10x Earth (1.08e+26 kg)
Radius
2.63x Earth (16,728 km)
This planet: 2.63× Earth radiusEarth: 1× (baseline)
Surface Gravity
2.63x Earth (25.8 m/s²)
Surface Temperature
320 K (47 °C / 117 °F)
Rotation Period
24.0 hours/day
This planet: 24 h/dayEarth: 24 h/day

Orbital Environment

Star Type
G-type (Yellow (Sun-like))
Distance from Star
0.63 AU (94.2 million km)
Orbital Period
183 days

Atmosphere

Hydrogen and helium dominated with trace methane and ammonia

Elemental Composition

H - Hydrogen
54.7%
O - Oxygen
24.9%
He - Helium
6.7%

Surface Characteristics

No solid surface - thick gaseous envelope with possible rocky core deep within
A binary star system's orrery: two suns close together, a red dashed dead-zone boundary, and a debris trail left by a destroyed world

New: Binary Star Systems 🌀

A system can now orbit two suns. Add a companion star when you build one — close, medium, or wide — and the physics decides what survives: a shared center of mass carves out a dead zone where gravity from both stars tears a world apart, leaving it as debris, and every surviving planet's orbit goes elliptical, moving fastest at closest approach and slowest out at aphelion. Push the separation to wide and the dead zone opens tens of AU across, wide enough to gut a system that would have been stable around one star alone. Stand on a world that made it through and you'll watch two suns cross the sky together.

Create your free account

Enter your email and we'll send a 6-digit code — no password needed.
We only keep your email and the username you choose. We never share or sell your email, and we don't send marketing — we use it only to email you a sign-in code. Read our privacy policy.

Send feedback

We're still building out the best experience we can — and we'd love your input. Tell us about features you enjoy, ideas you'd like to see, or pain points where something feels off, and we'll know where to look next.

Type
Idea
Bug
Pain point
Other