HD 205739 b
HD 205739 b is a cold gas giant orbiting HD 205739 in the constellation Piscis Austrinus. It lies about 302 light-years from Earth and was discovered in 2008 using the radial velocity method.
Is HD 205739 b in the Habitable Zone?
HD 205739 b orbits inside the inner edge of the habitable zone of HD 205739. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HD 205739: 1.109–2.588 AU (conservative: 1.404–2.454 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 205739 b — one full orbit around HD 205739 — lasts 279.8 Earth days, between the years of Mercury (88 days) and Earth (365 days). It orbits at an average distance of 0.896 AU — comparable to the inner Solar System. Its orbit is mildly elliptical (eccentricity 0.27).
How Was HD 205739 b Discovered?
HD 205739 b was discovered in 2008 using the radial velocity method, with observations from Las Campanas 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 205739 b?
HD 205739 b is 301.7 light-years (92.5 parsecs) from Earth. Light arriving here tonight left the planet around the year 1725. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 5,309,920 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 205739 b scores 0.30, ranking #1,495 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 205739
HD 205739
- Surface temperature
- 6,176 K (Sun: 5,772 K)
- Mass
- 1.22 M☉
- Radius
- 1.33 R☉
- Luminosity
- 2.2909 L☉
- Age
- 2.8 billion years (Sun: 4.6)
Planetary System
HD 205739 b is the only planet known to orbit HD 205739 so far.
HD 205739 b — Complete Data
| Mass (best estimate) | 435.41 Earth masses |
|---|---|
| Orbital period | 279.80 days |
| Orbital distance | 0.896 AU |
| Eccentricity | 0.270 |
| Earth Similarity Index | 0.30 |
| Distance from Earth | 301.7 light-years (92.5 parsecs) |
| Constellation | Piscis Austrinus |
| Discovery method | Radial Velocity |
| Discovery facility | Las Campanas Observatory |
| Discovery year | 2008 |
Data: NASA Exoplanet Archive, last updated 2014-09-25. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 205739 b
Is HD 205739 b habitable?
No — HD 205739 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HD 205739 b?
HD 205739 b is about 302 light-years from Earth in the constellation Piscis Austrinus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 5,309,920 years to get there.
How long is a year on HD 205739 b?
One orbit around HD 205739 takes 279.8 Earth days.
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