HD 4917 b
HD 4917 b is a cold gas giant orbiting HD 4917 in the constellation Cetus. It lies about 666 light-years from Earth and was discovered in 2018 using the radial velocity method.
Is HD 4917 b in the Habitable Zone?
HD 4917 b orbits inside the inner edge of the habitable zone of HD 4917. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HD 4917: 2.735–6.666 AU (conservative: 3.464–6.320 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 4917 b — one full orbit around HD 4917 — lasts 400.5 Earth days, longer than an Earth year. It orbits at an average distance of 1.167 AU. Its orbit is mildly elliptical (eccentricity 0.07).
How Was HD 4917 b Discovered?
HD 4917 b was discovered in 2018 using the radial velocity method, with observations from W. M. Keck 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 4917 b?
HD 4917 b is 666.3 light-years (204.3 parsecs) from Earth. Light arriving here tonight left the planet around the year 1360. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 11,726,880 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 4917 b scores 0.11, ranking #4,356 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 4917
HD 4917
- Surface temperature
- 4,802 K (Sun: 5,772 K)
- Mass
- 1.32 M☉
- Radius
- 5.01 R☉
Planetary System
HD 4917 b is the only planet known to orbit HD 4917 so far.
HD 4917 b — Complete Data
| Mass (best estimate) | 513.30 Earth masses |
|---|---|
| Orbital period | 400.50 days |
| Orbital distance | 1.167 AU |
| Eccentricity | 0.066 |
| Earth Similarity Index | 0.11 |
| Distance from Earth | 666.3 light-years (204.3 parsecs) |
| Constellation | Cetus |
| Discovery method | Radial Velocity |
| Discovery facility | W. M. Keck Observatory |
| Discovery year | 2018 |
Data: NASA Exoplanet Archive, last updated 2018-12-03. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 4917 b
Is HD 4917 b habitable?
No — HD 4917 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HD 4917 b?
HD 4917 b is about 666 light-years from Earth in the constellation Cetus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 11,726,880 years to get there.
How long is a year on HD 4917 b?
One orbit around HD 4917 takes 400.5 Earth days.
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