K2-3 d
Astrophysical Synthesis & Habitability Characterization
K2-3 d is a confirmed super-earth exoplanet orbiting the star K2-3, located approximately 143.7 light-years (44.07 parsecs) from the Solar System. First announced in 2015 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0599% across the stellar disk), this world measures 1.458 Earth radii and has a measured mass of 2.2 Earth masses. Combining its mass and radius yields a mean bulk density of 3.91 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.03 g⊕ (10.1 m/s²), and an escape velocity of 13.7 km/s.
In its orbital architecture around K2-3, K2-3 d completes one full revolution every 44.556 Earth days at a semi-major axis of 0.2014 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 49.2 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.091 carries the world between 0.1831 AU at periapsis and 0.2197 AU at apoapsis, driving measurable seasonal insolation cycles.
✓ Classified as a Temperate Habitable Zone Candidate.
With an estimated equilibrium temperature of 305 K (+32°C / +90°F) and an incident stellar irradiance of 1.44 S⊕ (~1,960 W/m²), K2-3 d orbits within the empirical circumstellar habitable zone where a rocky surface under sufficient atmospheric pressure can maintain liquid surface water.
The host star K2-3 is classified as a low-mass red dwarf of spectral type M V with an effective photospheric temperature of 3,844 K, a radius of 0.546 R☉, a mass of 0.549 M☉, an estimated bolometric luminosity of 0.058 L☉. Stellar evolution modeling indicates an estimated stellar age of 6.9 Gyr and a metallicity of [Fe/H] = -0.157 dex (metal-poor relative to the Sun). From Earth, K2-3 shines at apparent V-band magnitude 12.168 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The K2-3 system is a multi-planet architecture hosting 3 confirmed worlds, with K2-3 d sharing its stellar neighborhood alongside K2-3 b, K2-3 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 | K2-3 |
| Spectral Type | M V |
| Effective Temp (Teff) | 3,844 K |
| Stellar Radius | 0.5460 R☉ |
| Stellar Mass | 0.5490 M☉ |
| Bolometric Luminosity | 0.058 L☉ |
| Metallicity [Fe/H] | -0.157 dex |
| Stellar Age | 6.900 Gyr |
| Apparent Magnitude | V: 12.168 · G: 11.479 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.201400 AU |
| Orbital Period | 44.556 days |
| Mean Orbital Velocity | 49.2 km/s |
| Orbital Eccentricity (e) | 0.09100 |
| Orbital Inclination (i) | 89.8200° |
| Mean Bulk Density | 3.91 g/cm³ (13.7 km/s vesc) |
| Insolation Flux | 1.4400 S⊕ (~1,960 W/m²) |
| Habitable Zone Status | ★ Temperate Zone |
| Celestial Distance | 143.700 LY (44.073 pc) |