HD 176986 b
HD 176986 b is a super-Earth orbiting the K2.5 V star HD 176986 in the constellation Aquila. It lies about 91 light-years from Earth and was discovered in 2017 using the radial velocity method.
Is HD 176986 b in the Habitable Zone?
HD 176986 b orbits inside the inner edge of the habitable zone of HD 176986. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HD 176986: 0.452–1.096 AU (conservative: 0.573–1.039 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on HD 176986 b
The equilibrium temperature of HD 176986 b is about 767 K (494 °C) — hot enough to melt many metals. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C. It receives 81.70 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on HD 176986 b — one full orbit around HD 176986 — lasts 6.49 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.063 AU — closer to its star than Mercury is to the Sun.
How Was HD 176986 b Discovered?
HD 176986 b was discovered in 2017 using the radial velocity method, with observations from Multiple Observatories.
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 176986 b?
HD 176986 b is 90.6 light-years (27.8 parsecs) from Earth. Light arriving here tonight left the planet around the year 1936. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 1,594,560 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 176986 b scores 0.26, ranking #2,932 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 176986
HD 176986
- Spectral type
- K2.5 V
- Surface temperature
- 4,931 K (Sun: 5,772 K)
- Mass
- 0.79 M☉
- Radius
- 0.78 R☉
- Luminosity
- 0.3310 L☉
- Age
- 4.3 billion years (Sun: 4.6)
The HD 176986 Planetary System
HD 176986 b is one of 3 known planets in the HD 176986 system. Its siblings:
- HD 176986 c (Super Earth)
- HD 176986 d (Super Earth)
HD 176986 b — Complete Data
| Mass (best estimate) | 5.36 Earth masses |
|---|---|
| Orbital period | 6.49 days |
| Orbital distance | 0.063 AU |
| Equilibrium temperature | 767 K (494 °C) |
| Stellar irradiation | 81.70× Earth |
| Earth Similarity Index | 0.26 |
| Distance from Earth | 90.6 light-years (27.8 parsecs) |
| Constellation | Aquila |
| Discovery method | Radial Velocity |
| Discovery facility | Multiple Observatories |
| Discovery year | 2017 |
Data: NASA Exoplanet Archive, last updated 2026-02-12. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 176986 b
Is HD 176986 b habitable?
No — HD 176986 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HD 176986 b?
HD 176986 b is about 91 light-years from Earth in the constellation Aquila. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 1,594,560 years to get there.
How long is a year on HD 176986 b?
One orbit around HD 176986 takes 6.5 Earth days — short enough that 56 of its years would fit into one Earth year.
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