Kepler-204 b
Astrophysical Synthesis & Habitability Characterization
Kepler-204 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-204, located approximately 2239.8 light-years (686.72 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0351% across the stellar disk), this world measures 2.53 Earth radii and has a measured mass of 6.94 Earth masses. Combining its mass and radius yields a mean bulk density of 2.36 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 18.5 km/s.
In its orbital architecture around Kepler-204, Kepler-204 b completes one full revolution every 14.401 Earth days at a semi-major axis of 0.117 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 88.4 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.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 828 K (+555°C / +1031°F) and receiving 79.70 S⊕ (~108,476 W/m²), Kepler-204 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-204 is classified as a stellar host with an effective photospheric temperature of 5,812 K, a radius of 1.238 R☉, a mass of 1.038 M☉, an estimated bolometric luminosity of 1.569 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.41 Gyr and a metallicity of [Fe/H] = 0.07 dex (metal-rich relative to the Sun). From Earth, Kepler-204 shines at apparent V-band magnitude 13.977 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-204 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-204 b sharing its stellar neighborhood alongside Kepler-204 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-204 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,812 K |
| Stellar Radius | 1.2380 R☉ |
| Stellar Mass | 1.0380 M☉ |
| Bolometric Luminosity | 1.569 L☉ |
| Metallicity [Fe/H] | 0.070 dex |
| Stellar Age | 1.410 Gyr |
| Apparent Magnitude | V: 13.977 · G: 13.875 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.117000 AU |
| Orbital Period | 14.401 days |
| Mean Orbital Velocity | 88.4 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 86.4400° |
| Mean Bulk Density | 2.36 g/cm³ (18.5 km/s vesc) |
| Insolation Flux | 79.7030 S⊕ (~108,476 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2239.800 LY (686.723 pc) |