HD 231701 b
Astrophysical Synthesis & Habitability Characterization
HD 231701 b is a confirmed gas giant exoplanet orbiting the star HD 231701, located approximately 355.1 light-years (108.88 parsecs) from the Solar System. First announced in 2007 by W. M. Keck Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13.7 Earth radii (1.22 Jupiter radii) and has a measured mass of 359.148 Earth masses (1.13 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.77 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.91 g⊕ (18.73 m/s²), and an escape velocity of 57.3 km/s.
In its orbital architecture around HD 231701, HD 231701 b completes one full revolution every 141.63 Earth days at a semi-major axis of 0.567 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 43.6 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.13 carries the world between 0.4933 AU at periapsis and 0.6407 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 483 K (+210°C / +410°F) and receiving 9.18 S⊕ (~12,494 W/m²), HD 231701 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 231701 is classified as a warm F-type star of spectral type F8 V with an effective photospheric temperature of 6,101 K, a radius of 1.53 R☉, a mass of 1.21 M☉, an estimated bolometric luminosity of 2.91 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.43 Gyr and a metallicity of [Fe/H] = 0.05 dex (near-solar heavy-element abundance). From Earth, HD 231701 shines at apparent V-band magnitude 8.97 (accessible to binoculars and small amateur telescopes) in the Northern 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: W. M. Keck Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 231701 |
| Spectral Type | F8 V |
| Effective Temp (Teff) | 6,101 K |
| Stellar Radius | 1.5300 R☉ |
| Stellar Mass | 1.2100 M☉ |
| Bolometric Luminosity | 2.91 L☉ |
| Metallicity [Fe/H] | 0.050 dex |
| Stellar Age | 3.430 Gyr |
| Apparent Magnitude | V: 8.970 · G: 8.831 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.567000 AU |
| Orbital Period | 141.63 days |
| Mean Orbital Velocity | 43.6 km/s |
| Orbital Eccentricity (e) | 0.13000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.77 g/cm³ (57.3 km/s vesc) |
| Insolation Flux | 9.1798 S⊕ (~12,494 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 355.100 LY (108.877 pc) |