HD 103891 b
Astrophysical Synthesis & Habitability Characterization
HD 103891 b is a confirmed gas giant exoplanet orbiting the star HD 103891, located approximately 181.1 light-years (55.52 parsecs) from the Solar System. First announced in 2022 by La Silla Observatory 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 918.524 Earth masses (2.89 Jupiter masses). Combining its mass and radius yields a mean bulk density of 2.2 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 5.27 g⊕ (51.68 m/s²), and an escape velocity of 93.3 km/s.
In its orbital architecture around HD 103891, HD 103891 b completes one full revolution every 1919 Earth days (5.25Julian years) at a semi-major axis of 3.27 AU (corresponding to the middle-system regime between Mars at 1.52 AU and Jupiter at 5.20 AU). Its mean orbital velocity is approximately 18.5 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.31, swinging from 2.2563 AU at periapsis out to 4.2837 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 13.200 R⊕, HD 103891 b exceeds the empirical ~1.8–2.2 R⊕ Fulton radius valley threshold, indicating a substantial hydrogen-helium or supercritical volatile envelope without a conventional solid terrestrial surface.
The host star HD 103891 is classified as a warm F-type star of spectral type F9 with an effective photospheric temperature of 6,072 K, a radius of 2.22 R☉, a mass of 1.28 M☉, an estimated bolometric luminosity of 6.011 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.68 Gyr and a metallicity of [Fe/H] = -0.19 dex (metal-poor relative to the Sun). From Earth, HD 103891 shines at apparent V-band magnitude 6.595 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere.
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: La Silla Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 103891 |
| Spectral Type | F9 |
| Effective Temp (Teff) | 6,072 K |
| Stellar Radius | 2.2200 R☉ |
| Stellar Mass | 1.2800 M☉ |
| Bolometric Luminosity | 6.011 L☉ |
| Metallicity [Fe/H] | -0.190 dex |
| Stellar Age | 3.680 Gyr |
| Apparent Magnitude | V: 6.595 · G: 6.436 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 3.270000 AU |
| Orbital Period | 1919 days |
| Mean Orbital Velocity | 18.5 km/s |
| Orbital Eccentricity (e) | 0.31000 |
| Orbital Inclination (i) | 27.4000° |
| Mean Bulk Density | 2.2 g/cm³ (93.3 km/s vesc) |
| Insolation Flux | 0.5714 S⊕ (~778 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 181.100 LY (55.521 pc) |