HD 29399 b
Astrophysical Synthesis & Habitability Characterization
HD 29399 b is a confirmed gas giant exoplanet orbiting the star HD 29399, located approximately 144 light-years (44.15 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 13.5 Earth radii (1.2 Jupiter radii) and has a measured mass of 498.991 Earth masses (1.57 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.12 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 2.74 g⊕ (26.87 m/s²), and an escape velocity of 68 km/s.
In its orbital architecture around HD 29399, HD 29399 b completes one full revolution every 892.7 Earth days (2.44Julian years) at a semi-major axis of 1.913 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 23.3 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.05 carries the world between 1.8174 AU at periapsis and 2.0087 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 358 K (+85°C / +185°F) and receiving 2.74 S⊕ (~3,734 W/m²), HD 29399 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 29399 is classified as an orange K-type star of spectral type K1 III with an effective photospheric temperature of 4,845 K, a radius of 4.5 R☉, a mass of 1.17 M☉, an estimated bolometric luminosity of 10.011 L☉. Stellar evolution modeling indicates an estimated stellar age of 6.2 Gyr and a metallicity of [Fe/H] = 0.14 dex (metal-rich relative to the Sun). From Earth, HD 29399 shines at apparent V-band magnitude 5.79 (visible to the unaided human eye under dark skies) 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 29399 |
| Spectral Type | K1 III |
| Effective Temp (Teff) | 4,845 K |
| Stellar Radius | 4.5000 R☉ |
| Stellar Mass | 1.1700 M☉ |
| Bolometric Luminosity | 10.011 L☉ |
| Metallicity [Fe/H] | 0.140 dex |
| Stellar Age | 6.200 Gyr |
| Apparent Magnitude | V: 5.790 · G: 5.505 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.913000 AU |
| Orbital Period | 892.7 days |
| Mean Orbital Velocity | 23.3 km/s |
| Orbital Eccentricity (e) | 0.05000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.12 g/cm³ (68 km/s vesc) |
| Insolation Flux | 2.7435 S⊕ (~3,734 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 144.000 LY (44.152 pc) |