Kepler-281 b
Astrophysical Synthesis & Habitability Characterization
Kepler-281 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-281, located approximately 5692.9 light-years (1745.45 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0827% across the stellar disk), this world measures 2.82 Earth radii and has a measured mass of 324 Earth masses (1.02 Jupiter masses). Combining its mass and radius yields a mean bulk density of 79.66 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 40.74 g⊕ (399.52 m/s²), and an escape velocity of 119.9 km/s.
In its orbital architecture around Kepler-281, Kepler-281 b completes one full revolution every 14.646 Earth days at a semi-major axis of 0.117 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 86.9 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 694 K (+421°C / +790°F) and receiving 118.25 S⊕ (~160,933 W/m²), Kepler-281 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-281 is classified as a stellar host with an effective photospheric temperature of 5,723 K, a radius of 0.899 R☉, a mass of 0.95 M☉, an estimated bolometric luminosity of 0.778 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.6 Gyr and a metallicity of [Fe/H] = 0.02 dex (near-solar heavy-element abundance). From Earth, Kepler-281 shines at apparent V-band magnitude 15.931 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-281 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-281 b sharing its stellar neighborhood alongside Kepler-281 c, Kepler-281 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-281 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,723 K |
| Stellar Radius | 0.8990 R☉ |
| Stellar Mass | 0.9500 M☉ |
| Bolometric Luminosity | 0.778 L☉ |
| Metallicity [Fe/H] | 0.020 dex |
| Stellar Age | 0.600 Gyr |
| Apparent Magnitude | V: 15.931 · G: 15.754 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.117000 AU |
| Orbital Period | 14.646 days |
| Mean Orbital Velocity | 86.9 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 88.0900° |
| Mean Bulk Density | 79.66 g/cm³ (119.9 km/s vesc) |
| Insolation Flux | 118.2460 S⊕ (~160,933 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 5692.900 LY (1745.450 pc) |