GJ 9689 b
GJ 9689 b is a super-Earth orbiting the M0.5 star GJ 9689 in the constellation Aquila. It lies about 100 light-years from Earth and was discovered in 2020 using the radial velocity method.
Is GJ 9689 b in the Habitable Zone?
GJ 9689 b orbits inside the inner edge of the habitable zone of GJ 9689. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of GJ 9689: 0.204–0.522 AU (conservative: 0.259–0.495 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on GJ 9689 b
The equilibrium temperature of GJ 9689 b is about 453 K (180 °C) — hotter than anywhere on Earth. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C.
Orbit and Year Length
A year on GJ 9689 b — one full orbit around GJ 9689 — lasts 18.3 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.114 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.29).
How Was GJ 9689 b Discovered?
GJ 9689 b was discovered in 2020 using the radial velocity method, with observations from Roque de los Muchachos 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 GJ 9689 b?
GJ 9689 b is 99.9 light-years (30.6 parsecs) from Earth. Light arriving here tonight left the planet around the year 1927. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 1,758,240 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. GJ 9689 b scores 0.40, ranking #452 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: GJ 9689
GJ 9689
- Spectral type
- M0.5
- Surface temperature
- 3,836 K (Sun: 5,772 K)
- Mass
- 0.59 M☉
- Radius
- 0.57 R☉
- Luminosity
- 0.0631 L☉
- Age
- 8.9 billion years (Sun: 4.6)
Planetary System
GJ 9689 b is the only planet known to orbit GJ 9689 so far.
GJ 9689 b — Complete Data
| Mass (best estimate) | 9.65 Earth masses |
|---|---|
| Orbital period | 18.27 days |
| Orbital distance | 0.114 AU |
| Eccentricity | 0.290 |
| Equilibrium temperature | 453 K (180 °C) |
| Earth Similarity Index | 0.40 |
| Distance from Earth | 99.9 light-years (30.6 parsecs) |
| Constellation | Aquila |
| Discovery method | Radial Velocity |
| Discovery facility | Roque de los Muchachos Observatory |
| Discovery year | 2020 |
Data: NASA Exoplanet Archive, last updated 2021-10-25. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About GJ 9689 b
Is GJ 9689 b habitable?
No — GJ 9689 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is GJ 9689 b?
GJ 9689 b is about 100 light-years from Earth in the constellation Aquila. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 1,758,240 years to get there.
How long is a year on GJ 9689 b?
One orbit around GJ 9689 takes 18.3 Earth days — short enough that 20 of its years would fit into one Earth year.
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