91 Aqr b
91 Aqr b is a cold gas giant orbiting the K0 III star 91 Aqr in the constellation Aquarius. It lies about 144 light-years from Earth and was discovered in 2013 using the radial velocity method.
Is 91 Aqr b in the Habitable Zone?
91 Aqr b orbits inside the inner edge of the habitable zone of 91 Aqr. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of 91 Aqr: 5.699–13.975 AU (conservative: 7.219–13.249 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 91 Aqr b — one full orbit around 91 Aqr — lasts 181.4 Earth days, between the years of Mercury (88 days) and Earth (365 days). It orbits at an average distance of 0.700 AU — comparable to the inner Solar System. Its orbit is nearly circular (eccentricity 0.027).
How Was 91 Aqr b Discovered?
91 Aqr b was discovered in 2013 using the radial velocity method, with observations from Lick 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 91 Aqr b?
91 Aqr b is 143.6 light-years (44.0 parsecs) from Earth. Light arriving here tonight left the planet around the year 1883. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 2,527,360 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. 91 Aqr b scores 0.08, ranking #4,695 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: 91 Aqr
91 Aqr b belongs to a system of 3 stars; it orbits 91 Aqr.
91 Aqr
- Spectral type
- K0 III
- Surface temperature
- 4,665 K (Sun: 5,772 K)
- Mass
- 1.40 M☉
- Radius
- 11.00 R☉
- Age
- 3.6 billion years (Sun: 4.6)
Planetary System
91 Aqr b is the only planet known to orbit 91 Aqr so far.
91 Aqr b — Complete Data
| Mass (best estimate) | 1,017.00 Earth masses |
|---|---|
| Orbital period | 181.40 days |
| Orbital distance | 0.700 AU |
| Eccentricity | 0.027 |
| Earth Similarity Index | 0.08 |
| Distance from Earth | 143.6 light-years (44.0 parsecs) |
| Constellation | Aquarius |
| Discovery method | Radial Velocity |
| Discovery facility | Lick Observatory |
| Discovery year | 2013 |
Data: NASA Exoplanet Archive, last updated 2014-05-14. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About 91 Aqr b
Is 91 Aqr b habitable?
No — 91 Aqr b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is 91 Aqr b?
91 Aqr b is about 144 light-years from Earth in the constellation Aquarius. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 2,527,360 years to get there.
How long is a year on 91 Aqr b?
One orbit around 91 Aqr takes 181.4 Earth days.
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