HD 171238 b
HD 171238 b is a cold gas giant orbiting the G8 V star HD 171238 in the constellation Sagittarius. It lies about 146 light-years from Earth and was discovered in 2009 using the radial velocity method.
Is HD 171238 b in the Habitable Zone?
The position of HD 171238 b relative to the habitable zone of HD 171238 cannot be precisely determined from the available orbital data.
Orbit and Year Length
A year on HD 171238 b — one full orbit around HD 171238 — lasts 1,515.0 Earth days, longer than an Earth year. It orbits at an average distance of 2.518 AU. Its orbit is highly elliptical (eccentricity 0.36), swinging dramatically closer to and farther from its star.
How Was HD 171238 b Discovered?
HD 171238 b was discovered in 2009 using the radial velocity method, with observations from La Silla 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 171238 b?
HD 171238 b is 146.2 light-years (44.8 parsecs) from Earth. Light arriving here tonight left the planet around the year 1880. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 2,573,120 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 171238 b scores 0.19, ranking #4,007 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 171238
HD 171238
- Spectral type
- G8 V
- Mass
- 0.92 M☉
- Luminosity
- 0.6270 L☉
- Age
- 7.0 billion years (Sun: 4.6)
Planetary System
HD 171238 b is the only planet known to orbit HD 171238 so far.
HD 171238 b — Complete Data
| Mass | 2,796.89 Earth masses (8.800 Jupiter masses) |
|---|---|
| Orbital period | 1,515.00 days |
| Orbital distance | 2.518 AU |
| Eccentricity | 0.358 |
| Earth Similarity Index | 0.19 |
| Distance from Earth | 146.2 light-years (44.8 parsecs) |
| Constellation | Sagittarius |
| Discovery method | Radial Velocity |
| Discovery facility | La Silla Observatory |
| Discovery year | 2009 |
Data: NASA Exoplanet Archive, last updated 2022-06-27. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 171238 b
Is HD 171238 b habitable?
HD 171238 b is not known to orbit within the habitable zone of HD 171238, and as a cold gas giant it is an unlikely candidate for life as we know it.
How far away is HD 171238 b?
HD 171238 b is about 146 light-years from Earth in the constellation Sagittarius. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 2,573,120 years to get there.
How long is a year on HD 171238 b?
One orbit around HD 171238 takes 1,515.0 Earth days.
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