HD 212771 b
HD 212771 b is a cold gas giant orbiting HD 212771 in the constellation Aquarius. It lies about 363 light-years from Earth and was discovered in 2009 using the radial velocity method.
Is HD 212771 b in the Habitable Zone?
HD 212771 b orbits inside the inner edge of the habitable zone of HD 212771. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HD 212771: 3.094–7.480 AU (conservative: 3.919–7.092 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 212771 b — one full orbit around HD 212771 — lasts 380.7 Earth days, longer than an Earth year. It orbits at an average distance of 1.190 AU. Its orbit is mildly elliptical (eccentricity 0.08).
How Was HD 212771 b Discovered?
HD 212771 b was discovered in 2009 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 212771 b?
HD 212771 b is 362.5 light-years (111.2 parsecs) from Earth. Light arriving here tonight left the planet around the year 1664. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 6,380,000 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 212771 b scores 0.15, ranking #4,192 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 212771
HD 212771
- Surface temperature
- 5,003 K (Sun: 5,772 K)
- Mass
- 1.56 M☉
- Radius
- 5.27 R☉
Planetary System
HD 212771 b is the only planet known to orbit HD 212771 so far.
HD 212771 b — Complete Data
| Mass (best estimate) | 759.61 Earth masses |
|---|---|
| Orbital period | 380.70 days |
| Orbital distance | 1.190 AU |
| Eccentricity | 0.076 |
| Earth Similarity Index | 0.15 |
| Distance from Earth | 362.5 light-years (111.2 parsecs) |
| Constellation | Aquarius |
| Discovery method | Radial Velocity |
| Discovery facility | W. M. Keck Observatory |
| Discovery year | 2009 |
Data: NASA Exoplanet Archive, last updated 2018-12-03. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 212771 b
Is HD 212771 b habitable?
No — HD 212771 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HD 212771 b?
HD 212771 b is about 363 light-years from Earth in the constellation Aquarius. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 6,380,000 years to get there.
How long is a year on HD 212771 b?
One orbit around HD 212771 takes 380.7 Earth days.
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