HD 136352 d
Astrophysical Synthesis & Habitability Characterization
HD 136352 d is a confirmed sub-neptune exoplanet orbiting the star HD 136352, located approximately 47.9 light-years (14.68 parsecs) from the Solar System. First announced in 2019 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 2.562 Earth radii and has a measured mass of 8.82 Earth masses. Combining its mass and radius yields a mean bulk density of 2.89 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.34 g⊕ (13.14 m/s²), and an escape velocity of 20.8 km/s.
In its orbital architecture around HD 136352, HD 136352 d completes one full revolution every 107.245 Earth days at a semi-major axis of 0.425 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 43.1 km/s (compared to Earth's 29.8 km/s). The orbit is modeled as circular (e = 0.00), maintaining a constant stellar distance throughout its year.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 431 K (+158°C / +316°F) and receiving 5.74 S⊕ (~7,812 W/m²), HD 136352 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 136352 is classified as a solar-type yellow star of spectral type G4 V with an effective photospheric temperature of 5,664 K, a radius of 1.058 R☉, a mass of 0.87 M☉, an estimated bolometric luminosity of 1.034 L☉. Stellar evolution modeling indicates an estimated stellar age of 12.3 Gyr and a metallicity of [Fe/H] = -0.24 dex (metal-poor relative to the Sun). From Earth, HD 136352 shines at apparent V-band magnitude 5.65 (visible to the unaided human eye under dark skies) in the Southern celestial hemisphere. The HD 136352 system is a multi-planet architecture hosting 3 confirmed worlds, with HD 136352 d sharing its stellar neighborhood alongside HD 136352 b, HD 136352 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: La Silla Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 136352 |
| Spectral Type | G4 V |
| Effective Temp (Teff) | 5,664 K |
| Stellar Radius | 1.0580 R☉ |
| Stellar Mass | 0.8700 M☉ |
| Bolometric Luminosity | 1.034 L☉ |
| Metallicity [Fe/H] | -0.240 dex |
| Stellar Age | 12.300 Gyr |
| Apparent Magnitude | V: 5.650 · G: 5.485 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.425000 AU |
| Orbital Period | 107.245 days |
| Mean Orbital Velocity | 43.1 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.7300° |
| Mean Bulk Density | 2.89 g/cm³ (20.8 km/s vesc) |
| Insolation Flux | 5.7400 S⊕ (~7,812 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 47.900 LY (14.682 pc) |