HD 87646 b
HD 87646 b is a cold gas giant orbiting the G star HD 87646 in the constellation Leo. It lies about 240 light-years from Earth and was discovered in 2016 using the radial velocity method.
Is HD 87646 b in the Habitable Zone?
HD 87646 b orbits inside the inner edge of the habitable zone of HD 87646. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HD 87646: 1.161–2.735 AU (conservative: 1.470–2.593 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 87646 b — one full orbit around HD 87646 — lasts 13.5 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.117 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.05).
How Was HD 87646 b Discovered?
HD 87646 b was discovered in 2016 using the radial velocity method, with observations from Apache Point 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 87646 b?
HD 87646 b is 240.0 light-years (73.6 parsecs) from Earth. Light arriving here tonight left the planet around the year 1786. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 4,224,000 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 87646 b scores 0.07, ranking #4,848 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 87646
HD 87646 b belongs to a system of 3 stars; it orbits HD 87646.
HD 87646
- Spectral type
- G
- Surface temperature
- 5,770 K (Sun: 5,772 K)
- Mass
- 1.12 M☉
- Radius
- 1.55 R☉
Planetary System
HD 87646 b is the only planet known to orbit HD 87646 so far.
HD 87646 b — Complete Data
| Mass (best estimate) | 3,941.09 Earth masses |
|---|---|
| Orbital period | 13.48 days |
| Orbital distance | 0.117 AU |
| Eccentricity | 0.050 |
| Earth Similarity Index | 0.07 |
| Distance from Earth | 240.0 light-years (73.6 parsecs) |
| Constellation | Leo |
| Discovery method | Radial Velocity |
| Discovery facility | Apache Point Observatory |
| Discovery year | 2016 |
Data: NASA Exoplanet Archive, last updated 2016-08-17. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 87646 b
Is HD 87646 b habitable?
No — HD 87646 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HD 87646 b?
HD 87646 b is about 240 light-years from Earth in the constellation Leo. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 4,224,000 years to get there.
How long is a year on HD 87646 b?
One orbit around HD 87646 takes 13.5 Earth days — short enough that 27 of its years would fit into one Earth year.
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