Kepler-68 b
Astrophysical Synthesis & Habitability Characterization
Kepler-68 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-68, located approximately 470.2 light-years (144.17 parsecs) from the Solar System. First announced in 2013 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0296% across the stellar disk), this world measures 2.357 Earth radii and has a measured mass of 8.03 Earth masses. Combining its mass and radius yields a mean bulk density of 3.38 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.45 g⊕ (14.22 m/s²), and an escape velocity of 20.6 km/s.
In its orbital architecture around Kepler-68, Kepler-68 b completes one full revolution every 5.399 Earth days at a semi-major axis of 0.06135 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 123.6 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.09 carries the world between 0.0558 AU at periapsis and 0.0669 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1275 K (+1002°C / +1836°F) and receiving 441.00 S⊕ (~600,201 W/m²), Kepler-68 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-68 is classified as a stellar host with an effective photospheric temperature of 5,847 K, a radius of 1.2564 R☉, a mass of 1.057 M☉, an estimated bolometric luminosity of 1.655 L☉. Stellar evolution modeling indicates an estimated stellar age of 6.84 Gyr and a metallicity of [Fe/H] = 0.11 dex (metal-rich relative to the Sun). From Earth, Kepler-68 shines at apparent V-band magnitude 10.077 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-68 system is a multi-planet architecture hosting 4 confirmed worlds, with Kepler-68 b sharing its stellar neighborhood alongside Kepler-68 c, Kepler-68 d, Kepler-68 e.
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-68 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,847 K |
| Stellar Radius | 1.2564 R☉ |
| Stellar Mass | 1.0570 M☉ |
| Bolometric Luminosity | 1.655 L☉ |
| Metallicity [Fe/H] | 0.110 dex |
| Stellar Age | 6.840 Gyr |
| Apparent Magnitude | V: 10.077 · G: 9.934 |
| System Architecture | 2 Stars, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.061350 AU |
| Orbital Period | 5.399 days |
| Mean Orbital Velocity | 123.6 km/s |
| Orbital Eccentricity (e) | 0.09000 |
| Orbital Inclination (i) | 87.2300° |
| Mean Bulk Density | 3.38 g/cm³ (20.6 km/s vesc) |
| Insolation Flux | 441.0000 S⊕ (~600,201 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 470.200 LY (144.166 pc) |