Kepler-53 d
Astrophysical Synthesis & Habitability Characterization
Kepler-53 d is a confirmed sub-neptune exoplanet orbiting the star Kepler-53, located approximately 4455.5 light-years (1366.07 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0412% across the stellar disk), this world measures 2.12 Earth radii and has a measured mass of 166.503 Earth masses (0.52 Jupiter masses). Combining its mass and radius yields a mean bulk density of 96.36 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 37.05 g⊕ (363.34 m/s²), and an escape velocity of 99.1 km/s.
In its orbital architecture around Kepler-53, Kepler-53 d completes one full revolution every 9.752 Earth days at a semi-major axis of 0.091 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 101.5 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.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 870 K (+597°C / +1107°F) and receiving 144.85 S⊕ (~197,144 W/m²), Kepler-53 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-53 is classified as a stellar host with an effective photospheric temperature of 6,085 K, a radius of 0.958 R☉, a mass of 0.966 M☉, an estimated bolometric luminosity of 1.129 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.3 Gyr and a metallicity of [Fe/H] = 0 dex (near-solar heavy-element abundance). From Earth, Kepler-53 shines at apparent V-band magnitude 15.367 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-53 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-53 d sharing its stellar neighborhood alongside Kepler-53 b, Kepler-53 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-53 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,085 K |
| Stellar Radius | 0.9580 R☉ |
| Stellar Mass | 0.9660 M☉ |
| Bolometric Luminosity | 1.129 L☉ |
| Metallicity [Fe/H] | 0.000 dex |
| Stellar Age | 0.300 Gyr |
| Apparent Magnitude | V: 15.367 · G: 15.388 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.091000 AU |
| Orbital Period | 9.752 days |
| Mean Orbital Velocity | 101.5 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 80.9700° |
| Mean Bulk Density | 96.36 g/cm³ (99.1 km/s vesc) |
| Insolation Flux | 144.8520 S⊕ (~197,144 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 4455.500 LY (1366.070 pc) |