K2-16 c
Astrophysical Synthesis & Habitability Characterization
K2-16 c is a confirmed sub-neptune exoplanet orbiting the star K2-16, located approximately 1092.5 light-years (334.97 parsecs) from the Solar System. First announced in 2015 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.1245% across the stellar disk), this world measures 2.54 Earth radii and has a measured mass of 6.99 Earth masses. Combining its mass and radius yields a mean bulk density of 2.35 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.08 g⊕ (10.59 m/s²), and an escape velocity of 18.6 km/s.
In its orbital architecture around K2-16, K2-16 c completes one full revolution every 19.079 Earth days at a semi-major axis of 0.1229 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 70.1 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 485 K (+212°C / +414°F) and receiving 13.10 S⊕ (~17,829 W/m²), K2-16 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-16 is classified as an orange K-type star of spectral type K3 V with an effective photospheric temperature of 4,742 K, a radius of 0.66 R☉, a mass of 0.68 M☉, an estimated bolometric luminosity of 0.198 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.33 dex (metal-poor relative to the Sun). From Earth, K2-16 shines at apparent V-band magnitude 14.668 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The K2-16 system is a multi-planet architecture hosting 3 confirmed worlds, with K2-16 c sharing its stellar neighborhood alongside EPIC 201754305 d, K2-16 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 | K2-16 |
| Spectral Type | K3 V |
| Effective Temp (Teff) | 4,742 K |
| Stellar Radius | 0.6600 R☉ |
| Stellar Mass | 0.6800 M☉ |
| Bolometric Luminosity | 0.198 L☉ |
| Metallicity [Fe/H] | -0.330 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 14.668 · G: 14.323 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.122900 AU |
| Orbital Period | 19.079 days |
| Mean Orbital Velocity | 70.1 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 87.8300° |
| Mean Bulk Density | 2.35 g/cm³ (18.6 km/s vesc) |
| Insolation Flux | 13.1000 S⊕ (~17,829 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1092.500 LY (334.967 pc) |