Kepler-1521 b
Astrophysical Synthesis & Habitability Characterization
Kepler-1521 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-1521, located approximately 675.1 light-years (206.98 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0909% across the stellar disk), this world measures 2.5 Earth radii and has a measured mass of 6.8 Earth masses. Combining its mass and radius yields a mean bulk density of 2.4 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.09 g⊕ (10.69 m/s²), and an escape velocity of 18.4 km/s.
In its orbital architecture around Kepler-1521, Kepler-1521 b completes one full revolution every 47.148 Earth days at a semi-major axis of 0.23476 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 54.2 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 391 K (+118°C / +244°F) and receiving 5.12 S⊕ (~6,971 W/m²), Kepler-1521 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-1521 is classified as a stellar host with an effective photospheric temperature of 5,042 K, a radius of 0.76 R☉, a mass of 0.81 M☉, an estimated bolometric luminosity of 0.335 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.47 Gyr and a metallicity of [Fe/H] = -0.05 dex (near-solar heavy-element abundance). From Earth, Kepler-1521 shines at apparent V-band magnitude 13.049 (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-1521 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,042 K |
| Stellar Radius | 0.7600 R☉ |
| Stellar Mass | 0.8100 M☉ |
| Bolometric Luminosity | 0.335 L☉ |
| Metallicity [Fe/H] | -0.050 dex |
| Stellar Age | 4.470 Gyr |
| Apparent Magnitude | V: 13.049 · G: 12.848 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.234760 AU |
| Orbital Period | 47.148 days |
| Mean Orbital Velocity | 54.2 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.5800° |
| Mean Bulk Density | 2.4 g/cm³ (18.4 km/s vesc) |
| Insolation Flux | 5.1220 S⊕ (~6,971 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 675.100 LY (206.983 pc) |