KOI-55 c
Astrophysical Synthesis & Habitability Characterization
KOI-55 c is a confirmed terrestrial exoplanet orbiting the star KOI-55, located approximately 4015 light-years (1231.02 parsecs) from the Solar System. First announced in 2011 by Kepler using the Orbital Brightness Modulation detection technique, this world measures 0.867 Earth radii and has a measured mass of 0.655 Earth masses. Combining its mass and radius yields a mean bulk density of 5.54 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 0.87 g⊕ (8.53 m/s²), and an escape velocity of 9.7 km/s.
In its orbital architecture around KOI-55, KOI-55 c completes one full revolution every 0.343 Earth days at a semi-major axis of 0.0076 AU (an ultra-close orbit less than one-seventh of Mercury's 0.387 AU distance from the Sun, where strong stellar tidal forces typically induce synchronous rotation). Its mean orbital velocity is approximately 241.1 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 6911 K (+6638°C / +11980°F) and receiving 396,618.36 S⊕ (~539,797,589 W/m²), KOI-55 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star KOI-55 is classified as a massive B-type star of spectral type B with an effective photospheric temperature of 27,730 K, a radius of 0.203 R☉, a mass of 0.496 M☉, an estimated bolometric luminosity of 21.862 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.106 dex (metal-poor relative to the Sun). From Earth, KOI-55 shines at apparent V-band magnitude 15.154 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The KOI-55 system is a multi-planet architecture hosting 2 confirmed worlds, with KOI-55 c sharing its stellar neighborhood alongside KOI-55 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 | KOI-55 |
| Spectral Type | B |
| Effective Temp (Teff) | 27,730 K |
| Stellar Radius | 0.2030 R☉ |
| Stellar Mass | 0.4960 M☉ |
| Bolometric Luminosity | 21.862 L☉ |
| Metallicity [Fe/H] | -0.106 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 15.154 · G: 14.906 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.007600 AU |
| Orbital Period | 0.343 days |
| Mean Orbital Velocity | 241.1 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 65.0000° |
| Mean Bulk Density | 5.54 g/cm³ (9.7 km/s vesc) |
| Insolation Flux | 396618.3609 S⊕ (~539,797,589 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 4015.000 LY (1231.020 pc) |