The star
The star
Kepler-9
- Type
- yellow star
- Surface
- ≈ 5,774 K
- Size
- 0.96 × the Sun
- Mass
- 1.02 × the Sun
- Brightness
- 0.916 × the Sun
- Habitable zone
- 0.719–1.69 AU
The planets
Kepler-9
Kepler-9 d
- Year
- 1.59 days
- Distance from star
- 0.0273 AU
- Mass
- at least 8.4 Earths
- Size
- 1.6 × Earth
- Temperature
- ≈ 2026 K (+1753 °C)
- Found
- 2010, transit (Kepler)
Kepler-9
Kepler-9 b
- Year
- 19.24 days
- Distance from star
- 0.143 AU
- Mass
- 43 Earths
- Size
- 8.3 × Earth
- Temperature
- ≈ 661 K (+388 °C)
- Found
- 2010, transit (Kepler)
Kepler-9
Kepler-9 c
- Year
- 38.99 days
- Distance from star
- 0.227 AU
- Mass
- 30 Earths
- Size
- 8.1 × Earth
- Temperature
- ≈ 523 K (+250 °C)
- Found
- 2010, 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.