The star
The star
GJ 581
- Type
- M3.0 V
- Surface
- ≈ 3,500 K
- Size
- 0.30 × the Sun
- Mass
- 0.29 × the Sun
- Brightness
- 0.0124 × the Sun
- Habitable zone
- 0.091–0.236 AU
The planets
GJ 581
GJ 581 e
- Year
- 3.15 days
- Distance from star
- 0.028 AU
- Mass
- 2.5 Earths
- Size
- 1.4 × Earth
- Temperature
- ≈ 554 K (+281 °C)
- Found
- 2009, radial velocity (La Silla Observatory)
GJ 581
GJ 581 b
- Year
- 5.37 days
- Distance from star
- 0.0399 AU
- Mass
- 20 Earths
- Size
- 4.8 × Earth
- Temperature
- ≈ 464 K (+191 °C)
- Found
- 2005, radial velocity (La Silla Observatory)
GJ 581
GJ 581 c
- Year
- 12.92 days
- Distance from star
- 0.0718 AU
- Mass
- 6.8 Earths
- Size
- 2.5 × Earth
- Temperature
- ≈ 346 K (+73 °C)
- Found
- 2007, radial velocity (La Silla Observatory)
Masses found by the wobble method are minimums, because the orbit's tilt is unknown. Temperatures are equilibrium estimates for a bare planet, before any atmosphere.
How we know
The wobble
The planet tugs its star back and forth. Spectrographs measure the tiny shift in the star's light, which gives the planet's year and a minimum mass.
Sources
- Planet and star parameters: NASA Exoplanet Archive, Planetary Systems Composite Parameters, retrieved 31 Oct 2026. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with NASA under the Exoplanet Exploration Program.
- Position: HYG Database v4.1 (CC BY-SA 4.0).
- Habitable zone: a simple estimate from the star's brightness (√L × 0.95 to 1.67 AU), shown as a guide.