HD 161178 b
HD 161178 b is a cold gas giant orbiting the G9 III star HD 161178 in the constellation Draco. It lies about 350 light-years from Earth and was discovered in 2021 using the radial velocity method.
Is HD 161178 b in the Habitable Zone?
HD 161178 b orbits inside the inner edge of the habitable zone of HD 161178. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HD 161178: 5.937–14.483 AU (conservative: 7.521–13.731 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 161178 b — one full orbit around HD 161178 — lasts 279.3 Earth days, between the years of Mercury (88 days) and Earth (365 days). It orbits at an average distance of 0.850 AU — comparable to the inner Solar System. Its orbit is nearly circular (eccentricity 0.044).
How Was HD 161178 b Discovered?
HD 161178 b was discovered in 2021 using the radial velocity method, with observations from Okayama Astrophysical 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 161178 b?
HD 161178 b is 349.6 light-years (107.2 parsecs) from Earth. Light arriving here tonight left the planet around the year 1677. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 6,152,960 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 161178 b scores 0.08, ranking #4,732 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 161178
HD 161178
- Spectral type
- G9 III
- Surface temperature
- 4,786 K (Sun: 5,772 K)
- Mass
- 1.06 M☉
- Radius
- 10.95 R☉
- Luminosity
- 56.3599 L☉
Planetary System
HD 161178 b is the only planet known to orbit HD 161178 so far.
HD 161178 b — Complete Data
| Mass (best estimate) | 181.16 Earth masses |
|---|---|
| Orbital period | 279.30 days |
| Orbital distance | 0.850 AU |
| Eccentricity | 0.044 |
| Earth Similarity Index | 0.08 |
| Distance from Earth | 349.6 light-years (107.2 parsecs) |
| Constellation | Draco |
| Discovery method | Radial Velocity |
| Discovery facility | Okayama Astrophysical Observatory |
| Discovery year | 2021 |
Data: NASA Exoplanet Archive, last updated 2022-01-10. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 161178 b
Is HD 161178 b habitable?
No — HD 161178 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HD 161178 b?
HD 161178 b is about 350 light-years from Earth in the constellation Draco. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 6,152,960 years to get there.
How long is a year on HD 161178 b?
One orbit around HD 161178 takes 279.3 Earth days.
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