Kepler-196 d
Astrophysical Synthesis & Habitability Characterization
Kepler-196 d is a confirmed sub-neptune exoplanet orbiting the star Kepler-196, located approximately 1472 light-years (451.31 parsecs) from the Solar System. First announced in 2021 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.1004% across the stellar disk), this world measures 2.661 Earth radii and has a measured mass of 7.56 Earth masses. Combining its mass and radius yields a mean bulk density of 2.21 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.07 g⊕ (10.49 m/s²), and an escape velocity of 18.9 km/s.
In its orbital architecture around Kepler-196, Kepler-196 d completes one full revolution every 122.08 Earth days at a semi-major axis of 0.4545 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 40.5 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.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 2.661 R⊕, Kepler-196 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-196 is classified as a stellar host with an effective photospheric temperature of 5,132 K, a radius of 0.77 R☉, a mass of 0.805 M☉, an estimated bolometric luminosity of 0.369 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.09 Gyr and a metallicity of [Fe/H] = -0.06 dex (near-solar heavy-element abundance). From Earth, Kepler-196 shines at apparent V-band magnitude 14.239 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-196 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-196 d sharing its stellar neighborhood alongside Kepler-196 b, Kepler-196 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: Kepler · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | Kepler-196 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,132 K |
| Stellar Radius | 0.7700 R☉ |
| Stellar Mass | 0.8050 M☉ |
| Bolometric Luminosity | 0.369 L☉ |
| Metallicity [Fe/H] | -0.060 dex |
| Stellar Age | 3.090 Gyr |
| Apparent Magnitude | V: 14.239 · G: 14.103 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.454500 AU |
| Orbital Period | 122.08 days |
| Mean Orbital Velocity | 40.5 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.4000° |
| Mean Bulk Density | 2.21 g/cm³ (18.9 km/s vesc) |
| Insolation Flux | 1.8000 S⊕ (~2,450 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1472.000 LY (451.312 pc) |