HD 39855 b
HD 39855 b is a super-Earth orbiting the G8 V star HD 39855 in the constellation Lepus. It lies about 76 light-years from Earth and was discovered in 2019 using the radial velocity method.
Is HD 39855 b in the Habitable Zone?
The position of HD 39855 b relative to the habitable zone of HD 39855 cannot be precisely determined from the available orbital data.
Orbit and Year Length
A year on HD 39855 b — one full orbit around HD 39855 — lasts 3.25 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.041 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.14).
How Was HD 39855 b Discovered?
HD 39855 b was discovered in 2019 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 39855 b?
HD 39855 b is 75.9 light-years (23.3 parsecs) from Earth. Light arriving here tonight left the planet around the year 1951. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 1,335,840 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 39855 b scores 0.22, ranking #3,652 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 39855
HD 39855
- Spectral type
- G8 V
- Surface temperature
- 5,576 K (Sun: 5,772 K)
- Mass
- 0.87 M☉
Planetary System
HD 39855 b is the only planet known to orbit HD 39855 so far.
HD 39855 b — Complete Data
| Mass (best estimate) | 8.50 Earth masses |
|---|---|
| Orbital period | 3.25 days |
| Orbital distance | 0.041 AU |
| Eccentricity | 0.140 |
| Earth Similarity Index | 0.22 |
| Distance from Earth | 75.9 light-years (23.3 parsecs) |
| Constellation | Lepus |
| Discovery method | Radial Velocity |
| Discovery facility | Las Campanas Observatory |
| Discovery year | 2019 |
Data: NASA Exoplanet Archive, last updated 2019-05-20. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 39855 b
Is HD 39855 b habitable?
HD 39855 b is not known to orbit within the habitable zone of HD 39855, and as a super-Earth it is an unlikely candidate for life as we know it.
How far away is HD 39855 b?
HD 39855 b is about 76 light-years from Earth in the constellation Lepus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 1,335,840 years to get there.
How long is a year on HD 39855 b?
One orbit around HD 39855 takes 3.2 Earth days — short enough that 112 of its years would fit into one Earth year.
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