K2-37 d
Astrophysical Synthesis & Habitability Characterization
K2-37 d is a confirmed sub-neptune exoplanet orbiting the star K2-37, located approximately 586.9 light-years (179.94 parsecs) from the Solar System. First announced in 2016 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0685% across the stellar disk), this world measures 2.31 Earth radii and has a measured mass of 12.5 Earth masses. Combining its mass and radius yields a mean bulk density of 5.59 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 2.34 g⊕ (22.95 m/s²), and an escape velocity of 26 km/s.
In its orbital architecture around K2-37, K2-37 d completes one full revolution every 14.092 Earth days at a semi-major axis of 0.1102 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 85.1 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 646 K (+373°C / +703°F) and receiving 41.30 S⊕ (~56,209 W/m²), K2-37 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-37 is classified as a solar-type yellow star of spectral type G3 V with an effective photospheric temperature of 5,352 K, a radius of 0.809 R☉, a mass of 0.84 M☉, an estimated bolometric luminosity of 0.482 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.08 dex (near-solar heavy-element abundance). From Earth, K2-37 shines at apparent V-band magnitude 12.573 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The K2-37 system is a multi-planet architecture hosting 3 confirmed worlds, with K2-37 d sharing its stellar neighborhood alongside K2-37 b, K2-37 c.
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 | K2-37 |
| Spectral Type | G3 V |
| Effective Temp (Teff) | 5,352 K |
| Stellar Radius | 0.8090 R☉ |
| Stellar Mass | 0.8400 M☉ |
| Bolometric Luminosity | 0.482 L☉ |
| Metallicity [Fe/H] | -0.080 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 12.573 · G: 12.257 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.110200 AU |
| Orbital Period | 14.092 days |
| Mean Orbital Velocity | 85.1 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 89.1634° |
| Mean Bulk Density | 5.59 g/cm³ (26 km/s vesc) |
| Insolation Flux | 41.3000 S⊕ (~56,209 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 586.900 LY (179.943 pc) |