HD 159243 b
HD 159243 b is a cold gas giant orbiting the G0 V star HD 159243 in the constellation Ophiuchus. It lies about 239 light-years from Earth and was discovered in 2013 using the radial velocity method.
Is HD 159243 b in the Habitable Zone?
HD 159243 b orbits inside the inner edge of the habitable zone of HD 159243. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HD 159243: 0.838–1.958 AU (conservative: 1.061–1.857 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 159243 b — one full orbit around HD 159243 — lasts 12.6 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.110 AU — closer to its star than Mercury is to the Sun. Its orbit is nearly circular (eccentricity 0.020).
How Was HD 159243 b Discovered?
HD 159243 b was discovered in 2013 using the radial velocity method, with observations from Haute-Provence 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 159243 b?
HD 159243 b is 239.1 light-years (73.3 parsecs) from Earth. Light arriving here tonight left the planet around the year 1787. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 4,208,160 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 159243 b scores 0.08, ranking #4,777 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 159243
HD 159243
- Spectral type
- G0 V
- Surface temperature
- 6,123 K (Sun: 5,772 K)
- Mass
- 1.13 M☉
- Radius
- 1.12 R☉
- Luminosity
- 1.3002 L☉
- Age
- 1.3 billion years (Sun: 4.6)
The HD 159243 Planetary System
HD 159243 b is one of 2 known planets in the HD 159243 system. Its siblings:
- HD 159243 c (Cold Gas Giant)
HD 159243 b — Complete Data
| Mass (best estimate) | 359.13 Earth masses |
|---|---|
| Orbital period | 12.62 days |
| Orbital distance | 0.110 AU |
| Eccentricity | 0.020 |
| Earth Similarity Index | 0.08 |
| Distance from Earth | 239.1 light-years (73.3 parsecs) |
| Constellation | Ophiuchus |
| Discovery method | Radial Velocity |
| Discovery facility | Haute-Provence Observatory |
| Discovery year | 2013 |
Data: NASA Exoplanet Archive, last updated 2014-05-14. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 159243 b
Is HD 159243 b habitable?
No — HD 159243 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HD 159243 b?
HD 159243 b is about 239 light-years from Earth in the constellation Ophiuchus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 4,208,160 years to get there.
How long is a year on HD 159243 b?
One orbit around HD 159243 takes 12.6 Earth days — short enough that 29 of its years would fit into one Earth year.
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