HD 103197 b
Astrophysical Synthesis & Habitability Characterization
HD 103197 b is a confirmed sub-neptune exoplanet orbiting the star HD 103197, located approximately 186.4 light-years (57.15 parsecs) from the Solar System. First announced in 2011 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 5.83 Earth radii (0.52 Jupiter radii) and has a measured mass of 28.605 Earth masses. Combining its mass and radius yields a mean bulk density of 0.8 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.84 g⊕ (8.24 m/s²), and an escape velocity of 24.8 km/s.
In its orbital architecture around HD 103197, HD 103197 b completes one full revolution every 47.84 Earth days at a semi-major axis of 0.25 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 56.9 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 475 K (+202°C / +396°F) and receiving 7.52 S⊕ (~10,235 W/m²), HD 103197 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 103197 is classified as an orange K-type star of spectral type K1 V(P) with an effective photospheric temperature of 5,250 K, a radius of 0.88 R☉, a mass of 0.8 M☉, an estimated bolometric luminosity of 0.528 L☉. Stellar evolution modeling indicates an estimated stellar age of 9.1 Gyr and a metallicity of [Fe/H] = 0.22 dex (metal-rich relative to the Sun). From Earth, HD 103197 shines at apparent V-band magnitude 9.4 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere.
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: La Silla Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 103197 |
| Spectral Type | K1 V(P) |
| Effective Temp (Teff) | 5,250 K |
| Stellar Radius | 0.8800 R☉ |
| Stellar Mass | 0.8000 M☉ |
| Bolometric Luminosity | 0.528 L☉ |
| Metallicity [Fe/H] | 0.220 dex |
| Stellar Age | 9.100 Gyr |
| Apparent Magnitude | V: 9.400 · G: 9.164 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.250000 AU |
| Orbital Period | 47.84 days |
| Mean Orbital Velocity | 56.9 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.8 g/cm³ (24.8 km/s vesc) |
| Insolation Flux | 7.5200 S⊕ (~10,235 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 186.400 LY (57.146 pc) |