HD 218566 b
HD 218566 b is a cold gas giant orbiting HD 218566 in the constellation Pisces. It lies about 94 light-years from Earth and was discovered in 2010 using the radial velocity method. It orbits within the habitable zone of its star — the region where liquid water could exist on a planet's surface.
Is HD 218566 b in the Habitable Zone?
HD 218566 b orbits inside the conservative habitable zone of HD 218566 — the region where a rocky planet could sustain liquid water on its surface. This makes it one of the most interesting known exoplanets in the search for life.
Habitable zone of HD 218566: 0.452–1.104 AU (conservative: 0.572–1.047 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Orbit and Year Length
A year on HD 218566 b — one full orbit around HD 218566 — lasts 225.7 Earth days, between the years of Mercury (88 days) and Earth (365 days). It orbits at an average distance of 0.690 AU — comparable to the inner Solar System. Its orbit is highly elliptical (eccentricity 0.30), swinging dramatically closer to and farther from its star.
How Was HD 218566 b Discovered?
HD 218566 b was discovered in 2010 using the radial velocity method, with observations from W. M. Keck Observatory.
The radial velocity method measures the subtle wobble of a star caused by the gravitational pull of an orbiting planet, visible as periodic shifts in the star's light spectrum. The size of the wobble reveals the planet's minimum mass.
How Far Away Is HD 218566 b?
HD 218566 b is 94.0 light-years (28.8 parsecs) from Earth. Light arriving here tonight left the planet around the year 1932. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 1,654,400 years to make the journey.
Earth Similarity Index
The Earth Similarity Index (ESI) scores how physically similar a planet is to Earth, from 0 to 1, based on radius, density, escape velocity and surface temperature. HD 218566 b scores 0.42, ranking #407 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 218566
HD 218566
- Surface temperature
- 4,730 K (Sun: 5,772 K)
- Mass
- 0.76 M☉
- Radius
- 0.85 R☉
Planetary System
HD 218566 b is the only planet known to orbit HD 218566 so far.
HD 218566 b — Complete Data
| Mass (best estimate) | 63.57 Earth masses |
|---|---|
| Orbital period | 225.70 days |
| Orbital distance | 0.690 AU |
| Eccentricity | 0.300 |
| Earth Similarity Index | 0.42 |
| Distance from Earth | 94.0 light-years (28.8 parsecs) |
| Constellation | Pisces |
| Discovery method | Radial Velocity |
| Discovery facility | W. M. Keck Observatory |
| Discovery year | 2010 |
Data: NASA Exoplanet Archive, last updated 2018-09-04. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 218566 b
Is HD 218566 b habitable?
HD 218566 b orbits within the habitable zone of HD 218566, the region where liquid water could exist on a planet's surface. It sits in the conservative habitable zone — the most promising region for habitability. Whether it is actually habitable depends on its atmosphere and composition, which remain unknown.
How far away is HD 218566 b?
HD 218566 b is about 94 light-years from Earth in the constellation Pisces. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 1,654,400 years to get there.
How long is a year on HD 218566 b?
One orbit around HD 218566 takes 225.7 Earth days.
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