Kepler-598 c
Astrophysical Synthesis & Habitability Characterization
Kepler-598 c is a confirmed sub-neptune exoplanet orbiting the star Kepler-598, located approximately 2221.4 light-years (681.09 parsecs) from the Solar System. First announced in 2020 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0948% across the stellar disk), this world measures 3.024 Earth radii (0.27 Jupiter radii) and has a measured mass of 9.4 Earth masses. Combining its mass and radius yields a mean bulk density of 1.87 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.03 g⊕ (10.1 m/s²), and an escape velocity of 19.7 km/s.
In its orbital architecture around Kepler-598, Kepler-598 c completes one full revolution every 86.495 Earth days at a semi-major axis of 0.36672 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 46.1 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 367 K (+94°C / +201°F) and receiving 3.70 S⊕ (~5,036 W/m²), Kepler-598 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-598 is classified as a stellar host with an effective photospheric temperature of 5,245 K, a radius of 0.9003 R☉, a mass of 0.9 M☉, an estimated bolometric luminosity of 0.55 L☉. Stellar evolution modeling indicates an estimated stellar age of 12.3 Gyr and a metallicity of [Fe/H] = 0.03 dex (near-solar heavy-element abundance). From Earth, Kepler-598 shines at apparent V-band magnitude 14.829 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-598 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-598 c sharing its stellar neighborhood alongside Kepler-598 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-598 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,245 K |
| Stellar Radius | 0.9003 R☉ |
| Stellar Mass | 0.9000 M☉ |
| Bolometric Luminosity | 0.55 L☉ |
| Metallicity [Fe/H] | 0.030 dex |
| Stellar Age | 12.300 Gyr |
| Apparent Magnitude | V: 14.829 · G: 14.721 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.366720 AU |
| Orbital Period | 86.495 days |
| Mean Orbital Velocity | 46.1 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.3300° |
| Mean Bulk Density | 1.87 g/cm³ (19.7 km/s vesc) |
| Insolation Flux | 3.7000 S⊕ (~5,036 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2221.400 LY (681.086 pc) |