The star
The star
Kepler-398
- Type
- orange dwarf
- Surface
- ≈ 4,557 K
- Size
- 0.67 × the Sun
- Mass
- 0.72 × the Sun
- Brightness
- 0.155 × the Sun
- Habitable zone
- 0.314–0.773 AU
The planets
Kepler-398
Kepler-398 b
- Year
- 4.08 days
- Distance from star
- 0.044 AU
- Mass
- 0.75 Earths
- Size
- 0.93 × Earth
- Temperature
- ≈ 755 K (+482 °C)
- Found
- 2014, transit (Kepler)
Kepler-398
Kepler-398 d
- Year
- 6.83 days
- Distance from star
- 0.0618 AU
- Mass
- 0.61 Earths
- Size
- 0.88 × Earth
- Temperature
- ≈ 636 K (+363 °C)
- Found
- 2016, transit (Kepler)
Kepler-398
Kepler-398 c
- Year
- 11.42 days
- Distance from star
- 0.087 AU
- Mass
- 1 Earths
- Size
- 1 × Earth
- Temperature
- ≈ 536 K (+263 °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.