HIP 57274 d
Astrophysical Synthesis & Habitability Characterization
HIP 57274 d is a confirmed gas giant exoplanet orbiting the star HIP 57274, located approximately 84.3 light-years (25.86 parsecs) from the Solar System. First announced in 2011 by W. M. Keck Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 14.2 Earth radii (1.27 Jupiter radii) and has a measured mass of 167.4 Earth masses (0.53 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.32 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.83 g⊕ (8.14 m/s²), and an escape velocity of 38.4 km/s.
In its orbital architecture around HIP 57274, HIP 57274 d completes one full revolution every 431.7 Earth days (1.18Julian years) at a semi-major axis of 1.01 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 25.5 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.27, swinging from 0.7373 AU at periapsis out to 1.2827 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 14.200 R⊕, HIP 57274 d 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 HIP 57274 is classified as an orange K-type star of spectral type K4 V with an effective photospheric temperature of 4,640 K, a radius of 0.68 R☉, a mass of 0.73 M☉, an estimated bolometric luminosity of 0.192 L☉. Stellar evolution modeling indicates an estimated stellar age of 7.87 Gyr and a metallicity of [Fe/H] = 0.09 dex (metal-rich relative to the Sun). From Earth, HIP 57274 shines at apparent V-band magnitude 8.97 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The HIP 57274 system is a multi-planet architecture hosting 3 confirmed worlds, with HIP 57274 d sharing its stellar neighborhood alongside HIP 57274 b, HIP 57274 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: W. M. Keck Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HIP 57274 |
| Spectral Type | K4 V |
| Effective Temp (Teff) | 4,640 K |
| Stellar Radius | 0.6800 R☉ |
| Stellar Mass | 0.7300 M☉ |
| Bolometric Luminosity | 0.192 L☉ |
| Metallicity [Fe/H] | 0.090 dex |
| Stellar Age | 7.870 Gyr |
| Apparent Magnitude | V: 8.970 · G: 8.571 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.010000 AU |
| Orbital Period | 431.7 days |
| Mean Orbital Velocity | 25.5 km/s |
| Orbital Eccentricity (e) | 0.27000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.32 g/cm³ (38.4 km/s vesc) |
| Insolation Flux | 1.5183 S⊕ (~2,066 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 84.300 LY (25.862 pc) |