GJ 581 e
GJ 581 e is a super-Earth orbiting the M3.0 V star GJ 581 in the constellation Libra. It lies about 21 light-years from Earth and was discovered in 2009 using the radial velocity method.
Is GJ 581 e in the Habitable Zone?
GJ 581 e orbits inside the inner edge of the habitable zone of GJ 581. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of GJ 581: 0.091–0.236 AU (conservative: 0.115–0.224 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 GJ 581 e — one full orbit around GJ 581 — lasts 3.15 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.028 AU — closer to its star than Mercury is to the Sun. Its orbit is nearly circular (eccentricity 0.012).
How Was GJ 581 e Discovered?
GJ 581 e 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 GJ 581 e?
GJ 581 e is 20.5 light-years (6.3 parsecs) from Earth. Light arriving here tonight left the planet around the year 2006. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 360,800 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 581 e scores 0.37, ranking #614 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: GJ 581
GJ 581
- Spectral type
- M3.0 V
- Surface temperature
- 3,500 K (Sun: 5,772 K)
- Mass
- 0.30 M☉
- Radius
- 0.30 R☉
- Luminosity
- 0.0124 L☉
The GJ 581 Planetary System
GJ 581 e is one of 3 known planets in the GJ 581 system. Its siblings:
GJ 581 e — Complete Data
| Mass | 2.48 Earth masses (0.008 Jupiter masses) |
|---|---|
| Orbital period | 3.15 days |
| Orbital distance | 0.028 AU |
| Eccentricity | 0.012 |
| Earth Similarity Index | 0.37 |
| Distance from Earth | 20.5 light-years (6.3 parsecs) |
| Constellation | Libra |
| Discovery method | Radial Velocity |
| Discovery facility | La Silla Observatory |
| Discovery year | 2009 |
Data: NASA Exoplanet Archive, last updated 2025-03-03. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About GJ 581 e
Is GJ 581 e habitable?
No — GJ 581 e orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is GJ 581 e?
GJ 581 e is about 21 light-years from Earth in the constellation Libra. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 360,800 years to get there.
How long is a year on GJ 581 e?
One orbit around GJ 581 takes 3.1 Earth days — short enough that 116 of its years would fit into one Earth year.
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