HD 159243 b
Astrophysical Synthesis & Habitability Characterization
HD 159243 b is a confirmed gas giant exoplanet orbiting the star HD 159243, located approximately 239.1 light-years (73.31 parsecs) from the Solar System. First announced in 2013 by Haute-Provence 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 359.13 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 159243, HD 159243 b completes one full revolution every 12.62 Earth days at a semi-major axis of 0.11 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 94.8 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.02 (ranging from 0.1078 AU at periapsis to 0.1122 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 942 K (+669°C / +1236°F) and receiving 107.45 S⊕ (~146,242 W/m²), HD 159243 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 159243 is classified as a solar-type yellow star of spectral type G0 V with an effective photospheric temperature of 6,123 K, a radius of 1.12 R☉, a mass of 1.125 M☉, an estimated bolometric luminosity of 1.582 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.25 Gyr and a metallicity of [Fe/H] = 0.05 dex (near-solar heavy-element abundance). From Earth, HD 159243 shines at apparent V-band magnitude 8.65 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The HD 159243 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 159243 b sharing its stellar neighborhood alongside HD 159243 c.
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: Haute-Provence Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 159243 |
| Spectral Type | G0 V |
| Effective Temp (Teff) | 6,123 K |
| Stellar Radius | 1.1200 R☉ |
| Stellar Mass | 1.1250 M☉ |
| Bolometric Luminosity | 1.582 L☉ |
| Metallicity [Fe/H] | 0.050 dex |
| Stellar Age | 1.250 Gyr |
| Apparent Magnitude | V: 8.650 · G: 8.512 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.110000 AU |
| Orbital Period | 12.62 days |
| Mean Orbital Velocity | 94.8 km/s |
| Orbital Eccentricity (e) | 0.02000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.77 g/cm³ (57.3 km/s vesc) |
| Insolation Flux | 107.4520 S⊕ (~146,242 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 239.100 LY (73.306 pc) |