HD 221287 b
HD 221287 b is a cold gas giant orbiting HD 221287 in the constellation Tucana. It lies about 182 light-years from Earth and was discovered in 2007 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 221287 b in the Habitable Zone?
HD 221287 b orbits inside the conservative habitable zone of HD 221287 — 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 221287: 0.937–2.181 AU (conservative: 1.186–2.068 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 221287 b — one full orbit around HD 221287 — lasts 456.1 Earth days, longer than an Earth year. It orbits at an average distance of 1.250 AU. Its orbit is mildly elliptical (eccentricity 0.08).
How Was HD 221287 b Discovered?
HD 221287 b was discovered in 2007 using the radial velocity method, with observations from La Silla 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 221287 b?
HD 221287 b is 182.4 light-years (55.9 parsecs) from Earth. Light arriving here tonight left the planet around the year 1844. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 3,210,240 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 221287 b scores 0.39, ranking #505 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 221287
HD 221287
- Surface temperature
- 6,304 K (Sun: 5,772 K)
- Mass
- 1.25 M☉
- Luminosity
- 1.6600 L☉
- Age
- 1.3 billion years (Sun: 4.6)
Planetary System
HD 221287 b is the only planet known to orbit HD 221287 so far.
HD 221287 b — Complete Data
| Mass (best estimate) | 982.05 Earth masses |
|---|---|
| Orbital period | 456.10 days |
| Orbital distance | 1.250 AU |
| Eccentricity | 0.080 |
| Earth Similarity Index | 0.39 |
| Distance from Earth | 182.4 light-years (55.9 parsecs) |
| Constellation | Tucana |
| Discovery method | Radial Velocity |
| Discovery facility | La Silla Observatory |
| Discovery year | 2007 |
Data: NASA Exoplanet Archive, last updated 2014-05-14. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 221287 b
Is HD 221287 b habitable?
HD 221287 b orbits within the habitable zone of HD 221287, 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 221287 b?
HD 221287 b is about 182 light-years from Earth in the constellation Tucana. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 3,210,240 years to get there.
How long is a year on HD 221287 b?
One orbit around HD 221287 takes 456.1 Earth days.
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