Kepler-474 b
Astrophysical Synthesis & Habitability Characterization
Kepler-474 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-474, located approximately 2744.6 light-years (841.5 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0675% across the stellar disk), this world measures 3.06 Earth radii (0.27 Jupiter radii) and has a measured mass of 9.59 Earth masses. Combining its mass and radius yields a mean bulk density of 1.85 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.02 g⊕ (10 m/s²), and an escape velocity of 19.8 km/s.
In its orbital architecture around Kepler-474, Kepler-474 b completes one full revolution every 5.661 Earth days at a semi-major axis of 0.06092 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 117.1 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 1115 K (+842°C / +1548°F) and receiving 671.06 S⊕ (~913,318 W/m²), Kepler-474 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-474 is classified as a stellar host with an effective photospheric temperature of 5,785 K, a radius of 1.08 R☉, a mass of 0.99 M☉, an estimated bolometric luminosity of 1.172 L☉. Stellar evolution modeling indicates an estimated stellar age of 6.76 Gyr and a metallicity of [Fe/H] = -0.01 dex (near-solar heavy-element abundance). From Earth, Kepler-474 shines at apparent V-band magnitude 13.629 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.
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-474 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,785 K |
| Stellar Radius | 1.0800 R☉ |
| Stellar Mass | 0.9900 M☉ |
| Bolometric Luminosity | 1.172 L☉ |
| Metallicity [Fe/H] | -0.010 dex |
| Stellar Age | 6.760 Gyr |
| Apparent Magnitude | V: 13.629 · G: 13.469 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.060920 AU |
| Orbital Period | 5.661 days |
| Mean Orbital Velocity | 117.1 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 86.7700° |
| Mean Bulk Density | 1.85 g/cm³ (19.8 km/s vesc) |
| Insolation Flux | 671.0640 S⊕ (~913,318 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2744.600 LY (841.496 pc) |