HD 224018 d
HD 224018 d is a mini-Neptune orbiting the G V star HD 224018 in the constellation Aquarius. It lies about 344 light-years from Earth and was discovered in 2025 using the transit method.
How Big Is HD 224018 d?
HD 224018 d has a radius of 2.40 times that of Earth. Its mass is 4.2 times that of Earth, giving it a density of 1.70 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is HD 224018 d in the Habitable Zone?
HD 224018 d orbits inside the inner edge of the habitable zone of HD 224018. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HD 224018: 0.865–2.038 AU (conservative: 1.096–1.932 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on HD 224018 d
The equilibrium temperature of HD 224018 d is about 411 K (138 °C) — hotter than anywhere on Earth. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C.
Orbit and Year Length
A year on HD 224018 d — one full orbit around HD 224018 — lasts 138.1 Earth days, between the years of Mercury (88 days) and Earth (365 days). It orbits at an average distance of 0.530 AU — comparable to the inner Solar System. Its orbit is nearly circular (eccentricity 0.040).
How Was HD 224018 d Discovered?
HD 224018 d was discovered in 2025 using the transit method, with observations from K2.
The transit method watches a star for the tiny, regular dip in brightness that occurs when a planet crosses in front of it. The depth and timing of these dips reveal the planet's size and orbital period.
How Far Away Is HD 224018 d?
HD 224018 d is 344.0 light-years (105.5 parsecs) from Earth. Light arriving here tonight left the planet around the year 1682. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 6,054,400 years to make the journey.
The Host Star: HD 224018
HD 224018
- Spectral type
- G V
- Surface temperature
- 5,784 K (Sun: 5,772 K)
- Mass
- 1.01 M☉
- Radius
- 1.15 R☉
- Luminosity
- 1.3300 L☉
- Age
- 7.0 billion years (Sun: 4.6)
The HD 224018 Planetary System
HD 224018 d is one of 3 known planets in the HD 224018 system. Its siblings:
- HD 224018 b (Terrestrial)
- HD 224018 c (Super Earth)
HD 224018 d — Complete Data
| Radius | 2.400 Earth radii (0.214 Jupiter radii) |
|---|---|
| Mass | 4.20 Earth masses (0.013 Jupiter masses) |
| Density | 1.70 g/cm³ (Earth: 5.51) |
| Orbital period | 138.07 days |
| Orbital distance | 0.530 AU |
| Eccentricity | 0.040 |
| Equilibrium temperature | 411 K (138 °C) |
| Distance from Earth | 344.0 light-years (105.5 parsecs) |
| Constellation | Aquarius |
| Discovery method | Transit |
| Discovery facility | K2 |
| Discovery year | 2025 |
Data: NASA Exoplanet Archive, last updated 2025-09-17. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 224018 d
Is HD 224018 d habitable?
No — HD 224018 d orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HD 224018 d?
HD 224018 d is about 344 light-years from Earth in the constellation Aquarius. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 6,054,400 years to get there.
How big is HD 224018 d compared to Earth?
HD 224018 d has 2.40 times the radius of Earth and about 4.2 times its mass.
How long is a year on HD 224018 d?
One orbit around HD 224018 takes 138.1 Earth days.
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