HD 105618 c
Astrophysical Synthesis & Habitability Characterization
HD 105618 c is a confirmed gas giant exoplanet orbiting the star HD 105618, located approximately 228.6 light-years (70.08 parsecs) from the Solar System. First announced in 2022 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 11.9 Earth radii (1.06 Jupiter radii) and has a measured mass of 8419.592 Earth masses (26.49 Jupiter masses). Combining its mass and radius yields a mean bulk density of 27.55 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 59.46 g⊕ (583.1 m/s²), and an escape velocity of 297.5 km/s.
In its orbital architecture around HD 105618, HD 105618 c completes one full revolution every 77114.072 Earth days (211.13Julian years) at a semi-major axis of 35.731 AU (a wide outer-system orbit beyond Jupiter's 5.20 AU distance in our Solar System). Its mean orbital velocity is approximately 5 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.126 carries the world between 31.2289 AU at periapsis and 40.2331 AU at apoapsis, driving measurable seasonal insolation cycles.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 52 K (-221°C / -366°F) and an incident flux of 0.00 S⊕ (~2 W/m²), surface water and volatile species on HD 105618 c would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star HD 105618 is classified as a stellar host with an effective photospheric temperature of 5,671 K, a radius of 1.274 R☉, a mass of 1.01 M☉, an estimated bolometric luminosity of 1.506 L☉. From Earth, HD 105618 shines at apparent V-band magnitude 8.63 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The HD 105618 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 105618 c sharing its stellar neighborhood alongside HD 105618 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 105618 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,671 K |
| Stellar Radius | 1.2740 R☉ |
| Stellar Mass | 1.0100 M☉ |
| Bolometric Luminosity | 1.506 L☉ |
| Metallicity [Fe/H] | — |
| Stellar Age | — |
| Apparent Magnitude | V: 8.630 · G: 8.467 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 35.731000 AU |
| Orbital Period | 77114.072 days |
| Mean Orbital Velocity | 5 km/s |
| Orbital Eccentricity (e) | 0.12600 |
| Orbital Inclination (i) | 31.9680° |
| Mean Bulk Density | 27.55 g/cm³ (297.5 km/s vesc) |
| Insolation Flux | 0.0012 S⊕ (~2 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 228.600 LY (70.084 pc) |