HD 168009 b
HD 168009 b is a super-Earth orbiting HD 168009 in the constellation Lyra. It lies about 76 light-years from Earth and was discovered in 2021 using the radial velocity method.
Is HD 168009 b in the Habitable Zone?
HD 168009 b orbits inside the inner edge of the habitable zone of HD 168009. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HD 168009: 0.908–2.139 AU (conservative: 1.150–2.028 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 168009 b — one full orbit around HD 168009 — lasts 15.1 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.119 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.12).
How Was HD 168009 b Discovered?
HD 168009 b was discovered in 2021 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 168009 b?
HD 168009 b is 76.0 light-years (23.3 parsecs) from Earth. Light arriving here tonight left the planet around the year 1950. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 1,337,600 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 168009 b scores 0.22, ranking #3,651 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 168009
HD 168009
- Surface temperature
- 5,778 K (Sun: 5,772 K)
- Mass
- 0.99 M☉
- Radius
- 1.21 R☉
Planetary System
HD 168009 b is the only planet known to orbit HD 168009 so far.
HD 168009 b — Complete Data
| Mass (best estimate) | 9.53 Earth masses |
|---|---|
| Orbital period | 15.15 days |
| Orbital distance | 0.119 AU |
| Eccentricity | 0.120 |
| Earth Similarity Index | 0.22 |
| Distance from Earth | 76.0 light-years (23.3 parsecs) |
| Constellation | Lyra |
| Discovery method | Radial Velocity |
| Discovery facility | Multiple Observatories |
| Discovery year | 2021 |
Data: NASA Exoplanet Archive, last updated 2021-09-20. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 168009 b
Is HD 168009 b habitable?
No — HD 168009 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HD 168009 b?
HD 168009 b is about 76 light-years from Earth in the constellation Lyra. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 1,337,600 years to get there.
How long is a year on HD 168009 b?
One orbit around HD 168009 takes 15.1 Earth days — short enough that 24 of its years would fit into one Earth year.
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