HD 20003 b
HD 20003 b is a Neptune-like planet orbiting the G8 V star HD 20003 in the constellation Hydrus. It lies about 136 light-years from Earth and was discovered in 2019 using the radial velocity method.
Is HD 20003 b in the Habitable Zone?
HD 20003 b orbits inside the inner edge of the habitable zone of HD 20003. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HD 20003: 0.648–1.538 AU (conservative: 0.820–1.458 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 20003 b — one full orbit around HD 20003 — lasts 11.8 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.097 AU — closer to its star than Mercury is to the Sun. Its orbit is highly elliptical (eccentricity 0.36), swinging dramatically closer to and farther from its star.
How Was HD 20003 b Discovered?
HD 20003 b 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 20003 b?
HD 20003 b is 136.4 light-years (41.8 parsecs) from Earth. Light arriving here tonight left the planet around the year 1890. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 2,400,640 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 20003 b scores 0.21, ranking #3,796 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 20003
HD 20003
- Spectral type
- G8 V
- Surface temperature
- 5,494 K (Sun: 5,772 K)
- Mass
- 0.88 M☉
- Luminosity
- 0.7200 L☉
The HD 20003 Planetary System
HD 20003 b is one of 2 known planets in the HD 20003 system. Its siblings:
- HD 20003 c (Neptune-like)
HD 20003 b — Complete Data
| Mass (best estimate) | 11.66 Earth masses |
|---|---|
| Orbital period | 11.85 days |
| Orbital distance | 0.097 AU |
| Eccentricity | 0.360 |
| Earth Similarity Index | 0.21 |
| Distance from Earth | 136.4 light-years (41.8 parsecs) |
| Constellation | Hydrus |
| 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 20003 b
Is HD 20003 b habitable?
No — HD 20003 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HD 20003 b?
HD 20003 b is about 136 light-years from Earth in the constellation Hydrus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 2,400,640 years to get there.
How long is a year on HD 20003 b?
One orbit around HD 20003 takes 11.8 Earth days — short enough that 31 of its years would fit into one Earth year.
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