EPIC 212737443 c
Astrophysical Synthesis & Habitability Characterization
EPIC 212737443 c is a confirmed sub-neptune exoplanet orbiting the star EPIC 212737443, located approximately 1096.7 light-years (336.25 parsecs) from the Solar System. First announced in 2019 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.1343% across the stellar disk), this world measures 2.69 Earth radii and has a measured mass of 7.7 Earth masses. Combining its mass and radius yields a mean bulk density of 2.18 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.06 g⊕ (10.4 m/s²), and an escape velocity of 18.9 km/s.
In its orbital architecture around EPIC 212737443, EPIC 212737443 c completes one full revolution every 65.55 Earth days at a semi-major axis of 0.28 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 46.5 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.2 carries the world between 0.224 AU at periapsis and 0.336 AU at apoapsis, driving measurable seasonal insolation cycles.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 2.690 R⊕, EPIC 212737443 c exceeds the empirical ~1.8–2.2 R⊕ Fulton radius valley threshold, indicating a substantial hydrogen-helium or supercritical volatile envelope without a conventional solid terrestrial surface.
The host star EPIC 212737443 is classified as an orange K-type star of spectral type K3 with an effective photospheric temperature of 4,684 K, a radius of 0.673 R☉, a mass of 0.69 M☉, an estimated bolometric luminosity of 0.196 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.137 dex (metal-poor relative to the Sun). From Earth, EPIC 212737443 shines at apparent V-band magnitude 14.81 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The EPIC 212737443 system is a multi-planet architecture hosting 2 confirmed worlds, with EPIC 212737443 c sharing its stellar neighborhood alongside EPIC 212737443 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 | EPIC 212737443 |
| Spectral Type | K3 |
| Effective Temp (Teff) | 4,684 K |
| Stellar Radius | 0.6730 R☉ |
| Stellar Mass | 0.6900 M☉ |
| Bolometric Luminosity | 0.196 L☉ |
| Metallicity [Fe/H] | -0.137 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 14.810 · G: 14.478 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.280000 AU |
| Orbital Period | 65.55 days |
| Mean Orbital Velocity | 46.5 km/s |
| Orbital Eccentricity (e) | 0.20000 |
| Orbital Inclination (i) | 89.6300° |
| Mean Bulk Density | 2.18 g/cm³ (18.9 km/s vesc) |
| Insolation Flux | 2.2653 S⊕ (~3,083 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1096.700 LY (336.250 pc) |