HD 208897 b
HD 208897 b is a cold gas giant orbiting the K0 star HD 208897 in the constellation Pegasus. It lies about 220 light-years from Earth and was discovered in 2017 using the radial velocity method.
Is HD 208897 b in the Habitable Zone?
HD 208897 b orbits inside the inner edge of the habitable zone of HD 208897. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HD 208897: 2.765–6.724 AU (conservative: 3.502–6.375 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 208897 b — one full orbit around HD 208897 — lasts 358.3 Earth days, between the years of Mercury (88 days) and Earth (365 days). It orbits at an average distance of 1.063 AU — comparable to the inner Solar System. Its orbit is nearly circular (eccentricity 0.020).
How Was HD 208897 b Discovered?
HD 208897 b was discovered in 2017 using the radial velocity method, with observations from Multiple Observatories.
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 208897 b?
HD 208897 b is 220.1 light-years (67.5 parsecs) from Earth. Light arriving here tonight left the planet around the year 1806. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 3,873,760 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 208897 b scores 0.15, ranking #4,200 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 208897
HD 208897
- Spectral type
- K0
- Surface temperature
- 4,860 K (Sun: 5,772 K)
- Mass
- 1.25 M☉
- Radius
- 4.98 R☉
- Luminosity
- 12.3027 L☉
Planetary System
HD 208897 b is the only planet known to orbit HD 208897 so far.
HD 208897 b — Complete Data
| Mass (best estimate) | 379.49 Earth masses |
|---|---|
| Orbital period | 358.27 days |
| Orbital distance | 1.063 AU |
| Eccentricity | 0.020 |
| Earth Similarity Index | 0.15 |
| Distance from Earth | 220.1 light-years (67.5 parsecs) |
| Constellation | Pegasus |
| Discovery method | Radial Velocity |
| Discovery facility | Multiple Observatories |
| Discovery year | 2017 |
Data: NASA Exoplanet Archive, last updated 2023-09-19. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 208897 b
Is HD 208897 b habitable?
No — HD 208897 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HD 208897 b?
HD 208897 b is about 220 light-years from Earth in the constellation Pegasus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 3,873,760 years to get there.
How long is a year on HD 208897 b?
One orbit around HD 208897 takes 358.3 Earth days.
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