The star
The star
Kepler-81
- Type
- M0 V
- Surface
- ≈ 4,385 K
- Size
- 0.59 × the Sun
- Mass
- 0.64 × the Sun
- Brightness
- 0.129 × the Sun
- Habitable zone
- 0.288–0.716 AU
The planets
Kepler-81
Kepler-81 b
- Year
- 5.96 days
- Distance from star
- 0.0522 AU
- Mass
- 17 Earths
- Size
- 2.4 × Earth
- Temperature
- ≈ 635 K (+362 °C)
- Found
- 2012, transit (Kepler)
Kepler-81
Kepler-81 c
- Year
- 12.04 days
- Distance from star
- 0.0835 AU
- Mass
- 4.3 Earths
- Size
- 2.4 × Earth
- Temperature
- ≈ 502 K (+229 °C)
- Found
- 2012, transit (Kepler)
Kepler-81
Kepler-81 d
- Year
- 20.84 days
- Distance from star
- 0.128 AU
- Mass
- 1.9 Earths
- Size
- 1.2 × Earth
- Temperature
- ≈ 418 K (+145 °C)
- Found
- 2014, transit (Kepler)
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 shadow
The planet passes in front of its star and dims it by a fraction of a percent, every orbit. The dip gives the planet's size and year.
Sources
- Planet and star parameters: NASA Exoplanet Archive, Planetary Systems Composite Parameters, retrieved 1 Nov 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.