HD 93385 d
Astrophysical Synthesis & Habitability Characterization
HD 93385 d is a confirmed sub-neptune exoplanet orbiting the star HD 93385, located approximately 141.4 light-years (43.35 parsecs) from the Solar System. First announced in 2021 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 2.89 Earth radii and has a measured mass of 8.7 Earth masses. Combining its mass and radius yields a mean bulk density of 1.99 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.04 g⊕ (10.2 m/s²), and an escape velocity of 19.4 km/s.
In its orbital architecture around HD 93385, HD 93385 d completes one full revolution every 45.85 Earth days at a semi-major axis of 0.2565 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 60.9 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.09 carries the world between 0.2334 AU at periapsis and 0.2796 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 619 K (+346°C / +655°F) and receiving 24.47 S⊕ (~33,305 W/m²), HD 93385 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 93385 is classified as a solar-type yellow star of spectral type G2/G3 V with an effective photospheric temperature of 5,977 K, a radius of 1.1848 R☉, a mass of 1.04 M☉, an estimated bolometric luminosity of 1.607 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.3 Gyr and a metallicity of [Fe/H] = 0.02 dex (near-solar heavy-element abundance). From Earth, HD 93385 shines at apparent V-band magnitude 7.49 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere. The HD 93385 system is a multi-planet architecture hosting 3 confirmed worlds, with HD 93385 d sharing its stellar neighborhood alongside HD 93385 b, HD 93385 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 93385 |
| Spectral Type | G2/G3 V |
| Effective Temp (Teff) | 5,977 K |
| Stellar Radius | 1.1848 R☉ |
| Stellar Mass | 1.0400 M☉ |
| Bolometric Luminosity | 1.607 L☉ |
| Metallicity [Fe/H] | 0.020 dex |
| Stellar Age | 3.300 Gyr |
| Apparent Magnitude | V: 7.490 · G: 7.338 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.256500 AU |
| Orbital Period | 45.85 days |
| Mean Orbital Velocity | 60.9 km/s |
| Orbital Eccentricity (e) | 0.09000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.99 g/cm³ (19.4 km/s vesc) |
| Insolation Flux | 24.4710 S⊕ (~33,305 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 141.400 LY (43.348 pc) |