Kepler-645 b
Astrophysical Synthesis & Habitability Characterization
Kepler-645 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-645, located approximately 3827.7 light-years (1173.57 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0253% across the stellar disk), this world measures 2.1 Earth radii and has a measured mass of 5.06 Earth masses. Combining its mass and radius yields a mean bulk density of 3.01 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.15 g⊕ (11.28 m/s²), and an escape velocity of 17.4 km/s.
In its orbital architecture around Kepler-645, Kepler-645 b completes one full revolution every 3.276 Earth days at a semi-major axis of 0.04541 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 150.8 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 1730 K (+1457°C / +2655°F) and receiving 1,364.76 S⊕ (~1,857,441 W/m²), Kepler-645 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-645 is classified as a stellar host with an effective photospheric temperature of 6,170 K, a radius of 1.21 R☉, a mass of 1.13 M☉, an estimated bolometric luminosity of 1.904 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.95 Gyr and a metallicity of [Fe/H] = -0.01 dex (near-solar heavy-element abundance). From Earth, Kepler-645 shines at apparent V-band magnitude 13.944 (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-645 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,170 K |
| Stellar Radius | 1.2100 R☉ |
| Stellar Mass | 1.1300 M☉ |
| Bolometric Luminosity | 1.904 L☉ |
| Metallicity [Fe/H] | -0.010 dex |
| Stellar Age | 2.950 Gyr |
| Apparent Magnitude | V: 13.944 · G: 14.031 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.045410 AU |
| Orbital Period | 3.276 days |
| Mean Orbital Velocity | 150.8 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 82.5400° |
| Mean Bulk Density | 3.01 g/cm³ (17.4 km/s vesc) |
| Insolation Flux | 1364.7620 S⊕ (~1,857,441 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 3827.700 LY (1173.570 pc) |