K2-389 c
Astrophysical Synthesis & Habitability Characterization
K2-389 c is a confirmed sub-neptune exoplanet orbiting the star K2-389, located approximately 845.4 light-years (259.21 parsecs) from the Solar System. First announced in 2022 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0298% across the stellar disk), this world measures 2.04 Earth radii and has a measured mass of 4.82 Earth masses. Combining its mass and radius yields a mean bulk density of 3.13 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.16 g⊕ (11.38 m/s²), and an escape velocity of 17.2 km/s.
In its orbital architecture around K2-389, K2-389 c completes one full revolution every 20.851 Earth days.
ℹ️ Thermal & Atmospheric Regime: Current photometric and spectroscopic constraints for K2-389 c place it outside the conservative habitable zone definition pending further atmospheric characterization.
The host star K2-389 is classified as a solar-type yellow star of spectral type G3 with an effective photospheric temperature of 5,782 K, a radius of 1.084 R☉, a mass of 0.802 M☉, an estimated bolometric luminosity of 1.178 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.034 dex (near-solar heavy-element abundance). From Earth, K2-389 shines at apparent V-band magnitude 11.827 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The K2-389 system is a multi-planet architecture hosting 2 confirmed worlds, with K2-389 c sharing its stellar neighborhood alongside K2-389 b.
Methodology: Computed using the Schulze-Makuch et al. (2011) weighted metric comparing physical interior (radius, estimated density) and surface thermal regime (escape velocity, equilibrium temperature).
Discovery Facility: K2 · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | K2-389 |
| Spectral Type | G3 |
| Effective Temp (Teff) | 5,782 K |
| Stellar Radius | 1.0840 R☉ |
| Stellar Mass | 0.8020 M☉ |
| Bolometric Luminosity | 1.178 L☉ |
| Metallicity [Fe/H] | -0.034 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 11.827 · G: 11.570 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | — |
| Orbital Period | 20.851 days |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 3.13 g/cm³ (17.2 km/s vesc) |
| Insolation Flux | — |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 845.400 LY (259.208 pc) |