HD 27442 b
Astrophysical Synthesis & Habitability Characterization
HD 27442 b is a confirmed gas giant exoplanet orbiting the star HD 27442, located approximately 59.6 light-years (18.27 parsecs) from the Solar System. First announced in 2000 by Anglo-Australian Telescope 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 495.8 Earth masses (1.56 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.11 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 2.72 g⊕ (26.67 m/s²), and an escape velocity of 67.8 km/s.
In its orbital architecture around HD 27442, HD 27442 b completes one full revolution every 428.1 Earth days (1.17Julian years) at a semi-major axis of 1.271 AU (comparable to the inner terrestrial zone between Venus, Earth at 1.00 AU, and Mars at 1.52 AU). Its mean orbital velocity is approximately 32.3 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.06 carries the world between 1.1947 AU at periapsis and 1.3473 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 370 K (+97°C / +207°F) and receiving 4.39 S⊕ (~5,977 W/m²), HD 27442 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 27442 is classified as an orange K-type star of spectral type K1/2III with an effective photospheric temperature of 4,846 K, a radius of 3.18 R☉, a mass of 1.23 M☉, an estimated bolometric luminosity of 5.004 L☉. Stellar evolution modeling indicates an estimated stellar age of 10 Gyr and a metallicity of [Fe/H] = 0.42 dex (metal-rich relative to the Sun). From Earth, HD 27442 shines at apparent V-band magnitude 4.44 (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: Anglo-Australian Telescope · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 27442 |
| Spectral Type | K1/2III |
| Effective Temp (Teff) | 4,846 K |
| Stellar Radius | 3.1800 R☉ |
| Stellar Mass | 1.2300 M☉ |
| Bolometric Luminosity | 5.004 L☉ |
| Metallicity [Fe/H] | 0.420 dex |
| Stellar Age | 10.000 Gyr |
| Apparent Magnitude | V: 4.440 · G: 4.145 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.271000 AU |
| Orbital Period | 428.1 days |
| Mean Orbital Velocity | 32.3 km/s |
| Orbital Eccentricity (e) | 0.06000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.11 g/cm³ (67.8 km/s vesc) |
| Insolation Flux | 4.3915 S⊕ (~5,977 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 59.600 LY (18.270 pc) |