HD 27969 b
Astrophysical Synthesis & Habitability Characterization
HD 27969 b is a confirmed gas giant exoplanet orbiting the star HD 27969, located approximately 221.6 light-years (67.93 parsecs) from the Solar System. First announced in 2021 by Haute-Provence Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.9 Earth radii (1.15 Jupiter radii) and has a measured mass of 1525.576 Earth masses (4.8 Jupiter masses). Combining its mass and radius yields a mean bulk density of 3.92 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 9.17 g⊕ (89.93 m/s²), and an escape velocity of 121.6 km/s.
In its orbital architecture around HD 27969, HD 27969 b completes one full revolution every 654.5 Earth days (1.79Julian years) at a semi-major axis of 1.552 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 25.8 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.182 carries the world between 1.2695 AU at periapsis and 1.8345 AU at apoapsis, driving measurable seasonal insolation cycles.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 12.900 R⊕, HD 27969 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 27969 is classified as a solar-type yellow star of spectral type G0 V with an effective photospheric temperature of 5,966 K, a radius of 1.27 R☉, a mass of 1.16 M☉, an estimated bolometric luminosity of 1.833 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.18 dex (metal-rich relative to the Sun). From Earth, HD 27969 shines at apparent V-band magnitude 7.66 (accessible to binoculars and small amateur telescopes) in the Northern 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: Haute-Provence Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 27969 |
| Spectral Type | G0 V |
| Effective Temp (Teff) | 5,966 K |
| Stellar Radius | 1.2700 R☉ |
| Stellar Mass | 1.1600 M☉ |
| Bolometric Luminosity | 1.833 L☉ |
| Metallicity [Fe/H] | 0.180 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 7.660 · G: 7.514 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.552000 AU |
| Orbital Period | 654.5 days |
| Mean Orbital Velocity | 25.8 km/s |
| Orbital Eccentricity (e) | 0.18200 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 3.92 g/cm³ (121.6 km/s vesc) |
| Insolation Flux | 0.7600 S⊕ (~1,034 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 221.600 LY (67.933 pc) |