HD 154857 c
Astrophysical Synthesis & Habitability Characterization
HD 154857 c is a confirmed gas giant exoplanet orbiting the star HD 154857, located approximately 206.9 light-years (63.45 parsecs) from the Solar System. First announced in 2014 by Anglo-Australian Telescope using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13.2 Earth radii (1.18 Jupiter radii) and has a measured mass of 819.97 Earth masses (2.58 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.97 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 4.71 g⊕ (46.19 m/s²), and an escape velocity of 88.2 km/s.
In its orbital architecture around HD 154857, HD 154857 c completes one full revolution every 3452 Earth days (9.45Julian years) at a semi-major axis of 5.36 AU (a wide outer-system orbit beyond Jupiter's 5.20 AU distance in our Solar System). Its mean orbital velocity is approximately 16.9 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.06 carries the world between 5.0384 AU at periapsis and 5.6816 AU at apoapsis, driving measurable seasonal insolation cycles.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 155 K (-118°C / -180°F) and an incident flux of 0.16 S⊕ (~218 W/m²), surface water and volatile species on HD 154857 c would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star HD 154857 is classified as a solar-type yellow star of spectral type G5 V with an effective photospheric temperature of 5,605 K, a radius of 1.76 R☉, a mass of 1.718 M☉, an estimated bolometric luminosity of 2.743 L☉. Stellar evolution modeling indicates an estimated stellar age of 5.64 Gyr and a metallicity of [Fe/H] = -0.2 dex (metal-poor relative to the Sun). From Earth, HD 154857 shines at apparent V-band magnitude 7.24 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere. The HD 154857 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 154857 c sharing its stellar neighborhood alongside HD 154857 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: Anglo-Australian Telescope · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 154857 |
| Spectral Type | G5 V |
| Effective Temp (Teff) | 5,605 K |
| Stellar Radius | 1.7600 R☉ |
| Stellar Mass | 1.7180 M☉ |
| Bolometric Luminosity | 2.743 L☉ |
| Metallicity [Fe/H] | -0.200 dex |
| Stellar Age | 5.640 Gyr |
| Apparent Magnitude | V: 7.240 · G: 7.048 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 5.360000 AU |
| Orbital Period | 3452 days |
| Mean Orbital Velocity | 16.9 km/s |
| Orbital Eccentricity (e) | 0.06000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.97 g/cm³ (88.2 km/s vesc) |
| Insolation Flux | 0.1601 S⊕ (~218 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 206.900 LY (63.448 pc) |