KOBE-1 c
Astrophysical Synthesis & Habitability Characterization
KOBE-1 c is a confirmed sub-neptune exoplanet orbiting the star KOBE-1, located approximately 78.2 light-years (23.97 parsecs) from the Solar System. First announced in 2025 by Calar Alto Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 3.56 Earth radii (0.32 Jupiter radii) and has a measured mass of 12.4 Earth masses. Combining its mass and radius yields a mean bulk density of 1.52 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.98 g⊕ (9.61 m/s²), and an escape velocity of 20.9 km/s.
In its orbital architecture around KOBE-1, KOBE-1 c completes one full revolution every 29.671 Earth days at a semi-major axis of 0.16071 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 58.9 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 393 K (+120°C / +248°F) and receiving 3.91 S⊕ (~5,322 W/m²), KOBE-1 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star KOBE-1 is classified as an orange K-type star of spectral type K7 V with an effective photospheric temperature of 4,135 K, a radius of 0.619 R☉, a mass of 0.629 M☉, an estimated bolometric luminosity of 0.101 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.01 dex (near-solar heavy-element abundance). From Earth, KOBE-1 shines at apparent V-band magnitude 10.1 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The KOBE-1 system is a multi-planet architecture hosting 2 confirmed worlds, with KOBE-1 c sharing its stellar neighborhood alongside KOBE-1 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: Calar Alto Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | KOBE-1 |
| Spectral Type | K7 V |
| Effective Temp (Teff) | 4,135 K |
| Stellar Radius | 0.6190 R☉ |
| Stellar Mass | 0.6290 M☉ |
| Bolometric Luminosity | 0.101 L☉ |
| Metallicity [Fe/H] | -0.010 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 10.100 · G: 9.471 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.160710 AU |
| Orbital Period | 29.671 days |
| Mean Orbital Velocity | 58.9 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.52 g/cm³ (20.9 km/s vesc) |
| Insolation Flux | 3.9100 S⊕ (~5,322 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 78.200 LY (23.972 pc) |