HD 20794 b
HD 20794 b is a super-Earth orbiting the G6 V star HD 20794 in the constellation Eridanus. It lies about 20 light-years from Earth and was discovered in 2011 using the radial velocity method.
Is HD 20794 b in the Habitable Zone?
HD 20794 b orbits inside the inner edge of the habitable zone of HD 20794. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HD 20794: 0.637–1.519 AU (conservative: 0.807–1.440 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 20794 b — one full orbit around HD 20794 — lasts 18.3 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.126 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.06).
How Was HD 20794 b Discovered?
HD 20794 b was discovered in 2011 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 20794 b?
HD 20794 b is 19.6 light-years (6.0 parsecs) from Earth. Light arriving here tonight left the planet around the year 2007. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 344,960 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 20794 b scores 0.31, ranking #1,153 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 20794
HD 20794
- Spectral type
- G6 V
- Surface temperature
- 5,368 K (Sun: 5,772 K)
- Mass
- 0.79 M☉
- Radius
- 0.93 R☉
- Luminosity
- 0.6869 L☉
The HD 20794 Planetary System
HD 20794 b is one of 4 known planets in the HD 20794 system. Its siblings:
- HD 20794 d (Super Earth)
- HD 20794 e (Super Earth)
- HD 20794 f (Super Earth)
HD 20794 b — Complete Data
| Mass (best estimate) | 2.15 Earth masses |
|---|---|
| Orbital period | 18.31 days |
| Orbital distance | 0.126 AU |
| Eccentricity | 0.064 |
| Earth Similarity Index | 0.31 |
| Distance from Earth | 19.6 light-years (6.0 parsecs) |
| Constellation | Eridanus |
| Discovery method | Radial Velocity |
| Discovery facility | La Silla Observatory |
| Discovery year | 2011 |
Data: NASA Exoplanet Archive, last updated 2025-02-12. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 20794 b
Is HD 20794 b habitable?
No — HD 20794 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HD 20794 b?
HD 20794 b is about 20 light-years from Earth in the constellation Eridanus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 344,960 years to get there.
How long is a year on HD 20794 b?
One orbit around HD 20794 takes 18.3 Earth days — short enough that 20 of its years would fit into one Earth year.
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