Kepler-273 c
Astrophysical Synthesis & Habitability Characterization
Kepler-273 c is a confirmed super-earth exoplanet orbiting the star Kepler-273, located approximately 2328.6 light-years (713.96 parsecs) from the Solar System. First announced in 2014 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0496% across the stellar disk), this world measures 1.98 Earth radii and has a measured mass of 4.58 Earth masses. Combining its mass and radius yields a mean bulk density of 3.25 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.17 g⊕ (11.47 m/s²), and an escape velocity of 17 km/s.
In its orbital architecture around Kepler-273, Kepler-273 c completes one full revolution every 8.015 Earth days at a semi-major axis of 0.073 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 99.1 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 865 K (+592°C / +1098°F) and receiving 74.89 S⊕ (~101,921 W/m²), Kepler-273 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-273 is classified as a stellar host with an effective photospheric temperature of 5,626 K, a radius of 0.815 R☉, a mass of 0.756 M☉, an estimated bolometric luminosity of 0.597 L☉. Stellar evolution modeling indicates an estimated stellar age of 10.47 Gyr and a metallicity of [Fe/H] = -0.28 dex (metal-poor relative to the Sun). From Earth, Kepler-273 shines at apparent V-band magnitude 15.1 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-273 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-273 c sharing its stellar neighborhood alongside Kepler-273 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-273 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,626 K |
| Stellar Radius | 0.8150 R☉ |
| Stellar Mass | 0.7560 M☉ |
| Bolometric Luminosity | 0.597 L☉ |
| Metallicity [Fe/H] | -0.280 dex |
| Stellar Age | 10.470 Gyr |
| Apparent Magnitude | V: 15.100 · G: 14.968 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.073000 AU |
| Orbital Period | 8.015 days |
| Mean Orbital Velocity | 99.1 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 87.6900° |
| Mean Bulk Density | 3.25 g/cm³ (17 km/s vesc) |
| Insolation Flux | 74.8870 S⊕ (~101,921 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2328.600 LY (713.964 pc) |