Kepler-19 d
Astrophysical Synthesis & Habitability Characterization
Kepler-19 d is a confirmed sub-neptune exoplanet orbiting the star Kepler-19, located approximately 712.9 light-years (218.56 parsecs) from the Solar System. First announced in 2017 by Roque de los Muchachos Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 5.06 Earth radii (0.45 Jupiter radii) and has a measured mass of 22.5 Earth masses. Combining its mass and radius yields a mean bulk density of 0.96 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.88 g⊕ (8.63 m/s²), and an escape velocity of 23.6 km/s.
In its orbital architecture around Kepler-19, Kepler-19 d completes one full revolution every 62.95 Earth days. Its moderate orbital eccentricity of e = 0.05 driving measurable seasonal insolation cycles.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 5.060 R⊕, Kepler-19 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 Kepler-19 is classified as a stellar host with an effective photospheric temperature of 5,544 K, a radius of 0.859 R☉, a mass of 0.936 M☉, an estimated bolometric luminosity of 0.625 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.9 Gyr and a metallicity of [Fe/H] = -0.08 dex (near-solar heavy-element abundance). From Earth, Kepler-19 shines at apparent V-band magnitude 12.035 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-19 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-19 d sharing its stellar neighborhood alongside Kepler-19 b, Kepler-19 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: Roque de los Muchachos Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | Kepler-19 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,544 K |
| Stellar Radius | 0.8590 R☉ |
| Stellar Mass | 0.9360 M☉ |
| Bolometric Luminosity | 0.625 L☉ |
| Metallicity [Fe/H] | -0.080 dex |
| Stellar Age | 1.900 Gyr |
| Apparent Magnitude | V: 12.035 · G: 11.876 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | — |
| Orbital Period | 62.95 days |
| Orbital Eccentricity (e) | 0.05000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.96 g/cm³ (23.6 km/s vesc) |
| Insolation Flux | — |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 712.900 LY (218.562 pc) |