K2-285 d
Astrophysical Synthesis & Habitability Characterization
K2-285 d is a confirmed sub-neptune exoplanet orbiting the star K2-285, located approximately 505.4 light-years (154.96 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0835% across the stellar disk), this world measures 2.48 Earth radii and has a measured mass of 6.5 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 1.06 g⊕ (10.4 m/s²), and an escape velocity of 18.1 km/s.
In its orbital architecture around K2-285, K2-285 d completes one full revolution every 10.456 Earth days at a semi-major axis of 0.1178 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 122.6 km/s (compared to Earth's 29.8 km/s). The orbit is modeled as circular (e = 0.00), maintaining a constant stellar distance throughout its year.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 620 K (+347°C / +657°F) and receiving 24.61 S⊕ (~33,494 W/m²), K2-285 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-285 is classified as an orange K-type star of spectral type K2 V with an effective photospheric temperature of 4,975 K, a radius of 0.787 R☉, a mass of 0.83 M☉, an estimated bolometric luminosity of 0.34 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0 dex (near-solar heavy-element abundance). From Earth, K2-285 shines at apparent V-band magnitude 12.075 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The K2-285 system is a multi-planet architecture hosting 4 confirmed worlds, with K2-285 d sharing its stellar neighborhood alongside K2-285 b, K2-285 c, K2-285 e.
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 | K2-285 |
| Spectral Type | K2 V |
| Effective Temp (Teff) | 4,975 K |
| Stellar Radius | 0.7870 R☉ |
| Stellar Mass | 0.8300 M☉ |
| Bolometric Luminosity | 0.34 L☉ |
| Metallicity [Fe/H] | 0.000 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 12.075 · G: 11.804 |
| System Architecture | 1 Star, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.117800 AU |
| Orbital Period | 10.456 days |
| Mean Orbital Velocity | 122.6 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.6431° |
| Mean Bulk Density | 2.35 g/cm³ (18.1 km/s vesc) |
| Insolation Flux | 24.6100 S⊕ (~33,494 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 505.400 LY (154.961 pc) |