K2-219 d
Astrophysical Synthesis & Habitability Characterization
K2-219 d is a confirmed sub-neptune exoplanet orbiting the star K2-219, located approximately 1061.3 light-years (325.4 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0394% across the stellar disk), this world measures 2.576 Earth radii and has a measured mass of 7.16 Earth masses. Combining its mass and radius yields a mean bulk density of 2.31 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 K2-219, K2-219 d completes one full revolution every 11.137 Earth days.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 2.576 R⊕, K2-219 d 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 K2-219 is classified as a stellar host with an effective photospheric temperature of 5,753 K, a radius of 1.1892 R☉, a mass of 1.0215 M☉, an estimated bolometric luminosity of 1.39 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.13 dex (metal-rich relative to the Sun). From Earth, K2-219 shines at apparent V-band magnitude 12.09 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The K2-219 system is a multi-planet architecture hosting 3 confirmed worlds, with K2-219 d sharing its stellar neighborhood alongside K2-219 b, K2-219 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 | K2-219 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,753 K |
| Stellar Radius | 1.1892 R☉ |
| Stellar Mass | 1.0215 M☉ |
| Bolometric Luminosity | 1.39 L☉ |
| Metallicity [Fe/H] | 0.130 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 12.090 · G: 11.911 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | — |
| Orbital Period | 11.137 days |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 88.2866° |
| Mean Bulk Density | 2.31 g/cm³ (18.6 km/s vesc) |
| Insolation Flux | — |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1061.300 LY (325.400 pc) |