HD 180617 b
HD 180617 b is a Neptune-like planet orbiting HD 180617 in the constellation Aquila. It lies about 19 light-years from Earth and was discovered in 2018 using the radial velocity method. It orbits within the habitable zone of its star — the region where liquid water could exist on a planet's surface.
Is HD 180617 b in the Habitable Zone?
HD 180617 b orbits inside the conservative habitable zone of HD 180617 — the region where a rocky planet could sustain liquid water on its surface. This makes it one of the most interesting known exoplanets in the search for life.
Habitable zone of HD 180617: 0.147–0.381 AU (conservative: 0.186–0.361 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 180617 b — one full orbit around HD 180617 — lasts 105.9 Earth days, between the years of Mercury (88 days) and Earth (365 days). It orbits at an average distance of 0.343 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.10).
How Was HD 180617 b Discovered?
HD 180617 b was discovered in 2018 using the radial velocity method, with observations from Calar Alto 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 180617 b?
HD 180617 b is 19.3 light-years (5.9 parsecs) from Earth. Light arriving here tonight left the planet around the year 2007. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 339,680 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 180617 b scores 0.44, ranking #369 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 180617
HD 180617 b belongs to a system of 2 stars; it orbits HD 180617.
HD 180617
- Surface temperature
- 3,534 K (Sun: 5,772 K)
- Mass
- 0.48 M☉
- Radius
- 0.48 R☉
- Luminosity
- 0.0324 L☉
Planetary System
HD 180617 b is the only planet known to orbit HD 180617 so far.
HD 180617 b — Complete Data
| Mass (best estimate) | 12.21 Earth masses |
|---|---|
| Orbital period | 105.91 days |
| Orbital distance | 0.343 AU |
| Eccentricity | 0.101 |
| Earth Similarity Index | 0.44 |
| Distance from Earth | 19.3 light-years (5.9 parsecs) |
| Constellation | Aquila |
| Discovery method | Radial Velocity |
| Discovery facility | Calar Alto Observatory |
| Discovery year | 2018 |
Data: NASA Exoplanet Archive, last updated 2020-12-10. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 180617 b
Is HD 180617 b habitable?
HD 180617 b orbits within the habitable zone of HD 180617, the region where liquid water could exist on a planet's surface. It sits in the conservative habitable zone — the most promising region for habitability. Whether it is actually habitable depends on its atmosphere and composition, which remain unknown.
How far away is HD 180617 b?
HD 180617 b is about 19 light-years from Earth in the constellation Aquila. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 339,680 years to get there.
How long is a year on HD 180617 b?
One orbit around HD 180617 takes 105.9 Earth days.
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