HD 20781 e
HD 20781 e is a Neptune-like planet orbiting the K0 V star HD 20781 in the constellation Fornax. It lies about 117 light-years from Earth and was discovered in 2019 using the radial velocity method.
Is HD 20781 e in the Habitable Zone?
HD 20781 e orbits inside the inner edge of the habitable zone of HD 20781. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HD 20781: 0.541–1.296 AU (conservative: 0.686–1.229 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
See the full interactive habitable-zone view in the Exoplanet Explorer app ›
Orbit and Year Length
A year on HD 20781 e — one full orbit around HD 20781 — lasts 85.5 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.337 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.06).
How Was HD 20781 e Discovered?
HD 20781 e was discovered in 2019 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 20781 e?
HD 20781 e is 117.3 light-years (36.0 parsecs) from Earth. Light arriving here tonight left the planet around the year 1909. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 2,064,480 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 20781 e scores 0.40, ranking #496 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 20781
HD 20781 e belongs to a system of 2 stars; it orbits HD 20781.
HD 20781
- Spectral type
- K0 V
- Surface temperature
- 5,256 K (Sun: 5,772 K)
- Mass
- 0.70 M☉
- Luminosity
- 0.4900 L☉
The HD 20781 Planetary System
HD 20781 e is one of 4 known planets in the HD 20781 system. Its siblings:
- HD 20781 b (Terrestrial)
- HD 20781 c (Super Earth)
- HD 20781 d (Neptune-like)
HD 20781 e — Complete Data
| Mass (best estimate) | 14.03 Earth masses |
|---|---|
| Orbital period | 85.51 days |
| Orbital distance | 0.337 AU |
| Eccentricity | 0.060 |
| Earth Similarity Index | 0.40 |
| Distance from Earth | 117.3 light-years (36.0 parsecs) |
| Constellation | Fornax |
| Discovery method | Radial Velocity |
| Discovery facility | La Silla Observatory |
| Discovery year | 2019 |
Data: NASA Exoplanet Archive, last updated 2019-02-05. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 20781 e
Is HD 20781 e habitable?
No — HD 20781 e orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HD 20781 e?
HD 20781 e is about 117 light-years from Earth in the constellation Fornax. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 2,064,480 years to get there.
How long is a year on HD 20781 e?
One orbit around HD 20781 takes 85.5 Earth days.
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