Kepler-304 e
Astrophysical Synthesis & Habitability Characterization
Kepler-304 e is a confirmed terrestrial exoplanet orbiting the star Kepler-304, located approximately 1417.7 light-years (434.68 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0227% across the stellar disk), this world measures 1.2 Earth radii and has a measured mass of 1.87 Earth masses. Combining its mass and radius yields a mean bulk density of 5.97 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.3 g⊕ (12.75 m/s²), and an escape velocity of 14 km/s.
In its orbital architecture around Kepler-304, Kepler-304 e completes one full revolution every 1.499 Earth days at a semi-major axis of 0.02317 AU (an ultra-close orbit less than one-seventh of Mercury's 0.387 AU distance from the Sun, where strong stellar tidal forces typically induce synchronous rotation). Its mean orbital velocity is approximately 168.1 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 1137 K (+864°C / +1587°F) and receiving 397.25 S⊕ (~540,663 W/m²), Kepler-304 e orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-304 is classified as a stellar host with an effective photospheric temperature of 4,817 K, a radius of 0.73 R☉, a mass of 0.8 M☉, an estimated bolometric luminosity of 0.257 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.09 Gyr and a metallicity of [Fe/H] = 0.05 dex (near-solar heavy-element abundance). From Earth, Kepler-304 shines at apparent V-band magnitude 15.065 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-304 system is a multi-planet architecture hosting 4 confirmed worlds, with Kepler-304 e sharing its stellar neighborhood alongside Kepler-304 b, Kepler-304 c, Kepler-304 d.
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-304 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 4,817 K |
| Stellar Radius | 0.7300 R☉ |
| Stellar Mass | 0.8000 M☉ |
| Bolometric Luminosity | 0.257 L☉ |
| Metallicity [Fe/H] | 0.050 dex |
| Stellar Age | 2.090 Gyr |
| Apparent Magnitude | V: 15.065 · G: 14.831 |
| System Architecture | 1 Star, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.023170 AU |
| Orbital Period | 1.499 days |
| Mean Orbital Velocity | 168.1 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 87.5400° |
| Mean Bulk Density | 5.97 g/cm³ (14 km/s vesc) |
| Insolation Flux | 397.2540 S⊕ (~540,663 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1417.700 LY (434.684 pc) |