HD 147873 c
Astrophysical Synthesis & Habitability Characterization
HD 147873 c 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 13.3 Earth radii (1.19 Jupiter radii) and has a measured mass of 731.009 Earth masses (2.3 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.71 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 4.13 g⊕ (40.5 m/s²), and an escape velocity of 82.9 km/s.
In its orbital architecture around HD 147873, HD 147873 c completes one full revolution every 491.54 Earth days (1.35Julian years) at a semi-major axis of 1.36 AU (comparable to the inner terrestrial zone between Venus, Earth at 1.00 AU, and Mars at 1.52 AU). Its mean orbital velocity is approximately 30.1 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.23 carries the world between 1.0472 AU at periapsis and 1.6728 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 374 K (+101°C / +214°F) and receiving 3.24 S⊕ (~4,408 W/m²), HD 147873 c 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 c sharing its stellar neighborhood alongside HD 147873 b.
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) | 1.360000 AU |
| Orbital Period | 491.54 days |
| Mean Orbital Velocity | 30.1 km/s |
| Orbital Eccentricity (e) | 0.23000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.71 g/cm³ (82.9 km/s vesc) |
| Insolation Flux | 3.2385 S⊕ (~4,408 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 355.700 LY (109.055 pc) |