HD 147873 b
Astrophysical Synthesis & Habitability Characterization
HD 147873 b is a confirmed gas giant exoplanet orbiting the star HD 147873, located approximately 355.7 light-years (109.06 parsecs) from the Solar System. First announced in 2016 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.8 Earth radii (1.14 Jupiter radii) and has a measured mass of 1633.646 Earth masses (5.14 Jupiter masses). Combining its mass and radius yields a mean bulk density of 4.3 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 9.97 g⊕ (97.77 m/s²), and an escape velocity of 126.4 km/s.
In its orbital architecture around HD 147873, HD 147873 b completes one full revolution every 116.596 Earth days at a semi-major axis of 0.522 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 48.7 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.207 carries the world between 0.4139 AU at periapsis and 0.6301 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 603 K (+330°C / +626°F) and receiving 21.98 S⊕ (~29,919 W/m²), HD 147873 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 147873 is classified as a solar-type yellow star of spectral type G1 V with an effective photospheric temperature of 5,972 K, a radius of 2.29 R☉, a mass of 1.38 M☉, an estimated bolometric luminosity of 5.985 L☉. Stellar evolution modeling indicates an estimated stellar age of 4 Gyr and a metallicity of [Fe/H] = 0.03 dex (near-solar heavy-element abundance). From Earth, HD 147873 shines at apparent V-band magnitude 7.96 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere. The HD 147873 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 147873 b sharing its stellar neighborhood alongside HD 147873 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: Multiple Observatories · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 147873 |
| Spectral Type | G1 V |
| Effective Temp (Teff) | 5,972 K |
| Stellar Radius | 2.2900 R☉ |
| Stellar Mass | 1.3800 M☉ |
| Bolometric Luminosity | 5.985 L☉ |
| Metallicity [Fe/H] | 0.030 dex |
| Stellar Age | 4.000 Gyr |
| Apparent Magnitude | V: 7.960 · G: 7.818 |
| System Architecture | 2 Stars, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.522000 AU |
| Orbital Period | 116.596 days |
| Mean Orbital Velocity | 48.7 km/s |
| Orbital Eccentricity (e) | 0.20700 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 4.3 g/cm³ (126.4 km/s vesc) |
| Insolation Flux | 21.9829 S⊕ (~29,919 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 355.700 LY (109.055 pc) |