HD 212301 b
Astrophysical Synthesis & Habitability Characterization
HD 212301 b is a confirmed gas giant exoplanet orbiting the star HD 212301, located approximately 176.9 light-years (54.23 parsecs) from the Solar System. First announced in 2005 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 14.2 Earth radii (1.27 Jupiter radii) and has a measured mass of 162.093 Earth masses (0.51 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.31 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.8 g⊕ (7.85 m/s²), and an escape velocity of 37.8 km/s.
In its orbital architecture around HD 212301, HD 212301 b completes one full revolution every 2.246 Earth days at a semi-major axis of 0.03 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 145.3 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 1871 K (+1598°C / +2908°F) and receiving 1,944.44 S⊕ (~2,646,389 W/m²), HD 212301 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 212301 is classified as a warm F-type star of spectral type F8 V with an effective photospheric temperature of 6,239 K, a radius of 1.16 R☉, a mass of 1.55 M☉, an estimated bolometric luminosity of 1.829 L☉. Stellar evolution modeling indicates an estimated stellar age of 1 Gyr and a metallicity of [Fe/H] = 0.18 dex (metal-rich relative to the Sun). From Earth, HD 212301 shines at apparent V-band magnitude 7.76 (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 212301 |
| Spectral Type | F8 V |
| Effective Temp (Teff) | 6,239 K |
| Stellar Radius | 1.1600 R☉ |
| Stellar Mass | 1.5500 M☉ |
| Bolometric Luminosity | 1.829 L☉ |
| Metallicity [Fe/H] | 0.180 dex |
| Stellar Age | 1.000 Gyr |
| Apparent Magnitude | V: 7.760 · G: 7.635 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.030000 AU |
| Orbital Period | 2.246 days |
| Mean Orbital Velocity | 145.3 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.31 g/cm³ (37.8 km/s vesc) |
| Insolation Flux | 1944.4444 S⊕ (~2,646,389 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 176.900 LY (54.230 pc) |