HD 105618 b
Astrophysical Synthesis & Habitability Characterization
HD 105618 b is a confirmed sub-neptune 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 5.44 Earth radii (0.49 Jupiter radii) and has a measured mass of 25.426 Earth masses. Combining its mass and radius yields a mean bulk density of 0.87 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.86 g⊕ (8.43 m/s²), and an escape velocity of 24.2 km/s.
In its orbital architecture around HD 105618, HD 105618 b completes one full revolution every 10.022 Earth days at a semi-major axis of 0.091 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 98.8 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.455, swinging from 0.0496 AU at periapsis out to 0.1324 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1023 K (+750°C / +1382°F) and receiving 182.63 S⊕ (~248,566 W/m²), HD 105618 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
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 b sharing its stellar neighborhood alongside HD 105618 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 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) | 0.091000 AU |
| Orbital Period | 10.022 days |
| Mean Orbital Velocity | 98.8 km/s |
| Orbital Eccentricity (e) | 0.45500 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.87 g/cm³ (24.2 km/s vesc) |
| Insolation Flux | 182.6347 S⊕ (~248,566 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 228.600 LY (70.084 pc) |