HD 90156 b
HD 90156 b is a Neptune-like planet orbiting HD 90156 in the constellation Hydra. It lies about 72 light-years from Earth and was discovered in 2009 using the radial velocity method.
Is HD 90156 b in the Habitable Zone?
HD 90156 b orbits inside the inner edge of the habitable zone of HD 90156. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HD 90156: 0.644–1.524 AU (conservative: 0.815–1.445 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 90156 b — one full orbit around HD 90156 — lasts 49.8 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.250 AU — closer to its star than Mercury is to the Sun. Its orbit is highly elliptical (eccentricity 0.31), swinging dramatically closer to and farther from its star.
How Was HD 90156 b Discovered?
HD 90156 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 90156 b?
HD 90156 b is 71.6 light-years (21.9 parsecs) from Earth. Light arriving here tonight left the planet around the year 1955. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 1,260,160 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 90156 b scores 0.25, ranking #3,041 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 90156
HD 90156
- Surface temperature
- 5,599 K (Sun: 5,772 K)
- Mass
- 0.84 M☉
- Luminosity
- 0.7200 L☉
- Age
- 4.4 billion years (Sun: 4.6)
Planetary System
HD 90156 b is the only planet known to orbit HD 90156 so far.
HD 90156 b — Complete Data
| Mass (best estimate) | 17.98 Earth masses |
|---|---|
| Orbital period | 49.77 days |
| Orbital distance | 0.250 AU |
| Eccentricity | 0.310 |
| Earth Similarity Index | 0.25 |
| Distance from Earth | 71.6 light-years (21.9 parsecs) |
| Constellation | Hydra |
| Discovery method | Radial Velocity |
| Discovery facility | La Silla Observatory |
| Discovery year | 2009 |
Data: NASA Exoplanet Archive, last updated 2014-05-14. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 90156 b
Is HD 90156 b habitable?
No — HD 90156 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HD 90156 b?
HD 90156 b is about 72 light-years from Earth in the constellation Hydra. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 1,260,160 years to get there.
How long is a year on HD 90156 b?
One orbit around HD 90156 takes 49.8 Earth days.
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