Kepler-280 c
Astrophysical Synthesis & Habitability Characterization
Kepler-280 c is a confirmed sub-neptune exoplanet orbiting the star Kepler-280, located approximately 2545.2 light-years (780.36 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0433% across the stellar disk), this world measures 2.01 Earth radii and has a measured mass of 4.7 Earth masses. Combining its mass and radius yields a mean bulk density of 3.19 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.16 g⊕ (11.38 m/s²), and an escape velocity of 17.1 km/s.
In its orbital architecture around Kepler-280, Kepler-280 c completes one full revolution every 4.807 Earth days at a semi-major axis of 0.056 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 126.7 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 1088 K (+815°C / +1499°F) and receiving 279.09 S⊕ (~379,835 W/m²), Kepler-280 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-280 is classified as a stellar host with an effective photospheric temperature of 5,744 K, a radius of 0.886 R☉, a mass of 0.962 M☉, an estimated bolometric luminosity of 0.767 L☉. Stellar evolution modeling indicates an estimated stellar age of 5.62 Gyr and a metallicity of [Fe/H] = 0.121 dex (metal-rich relative to the Sun). From Earth, Kepler-280 shines at apparent V-band magnitude 14.35 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-280 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-280 c sharing its stellar neighborhood alongside Kepler-280 b.
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-280 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,744 K |
| Stellar Radius | 0.8860 R☉ |
| Stellar Mass | 0.9620 M☉ |
| Bolometric Luminosity | 0.767 L☉ |
| Metallicity [Fe/H] | 0.121 dex |
| Stellar Age | 5.620 Gyr |
| Apparent Magnitude | V: 14.350 · G: 14.457 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.056000 AU |
| Orbital Period | 4.807 days |
| Mean Orbital Velocity | 126.7 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 86.6500° |
| Mean Bulk Density | 3.19 g/cm³ (17.1 km/s vesc) |
| Insolation Flux | 279.0850 S⊕ (~379,835 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2545.200 LY (780.361 pc) |