The star
The star
K2-239
- Type
- M3.0 V
- Surface
- ≈ 3,420 K
- Size
- 0.36 × the Sun
- Mass
- 0.40 × the Sun
- Brightness
- 0.016 × the Sun
- Habitable zone
- 0.104–0.27 AU
The planets
K2-239
K2-239 b
- Year
- 5.24 days
- Distance from star
- 0.0441 AU
- Mass
- 1.4 Earths
- Size
- 1.1 × Earth
- Temperature
- ≈ 502 K (+229 °C)
- Found
- 2018, transit (K2)
K2-239
K2-239 c
- Year
- 7.78 days
- Distance from star
- 0.0576 AU
- Mass
- 0.97 Earths
- Size
- 1 × Earth
- Temperature
- ≈ 427 K (+154 °C)
- Found
- 2018, transit (K2)
K2-239
K2-239 d
- Year
- 10.12 days
- Distance from star
- 0.0685 AU
- Mass
- 1.4 Earths
- Size
- 1.1 × Earth
- Temperature
- ≈ 399 K (+126 °C)
- Found
- 2018, transit (K2)
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.