HD 285968 b
Astrophysical Synthesis & Habitability Characterization
HD 285968 b is a confirmed sub-neptune exoplanet orbiting the star HD 285968, located approximately 30.9 light-years (9.47 parsecs) from the Solar System. First announced in 2008 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 2.83 Earth radii and has a measured mass of 8.4 Earth masses. Combining its mass and radius yields a mean bulk density of 2.04 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.05 g⊕ (10.3 m/s²), and an escape velocity of 19.3 km/s.
In its orbital architecture around HD 285968, HD 285968 b completes one full revolution every 8.784 Earth days at a semi-major axis of 0.066 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 81.7 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 450 K (+177°C / +351°F) and receiving 5.05 S⊕ (~6,867 W/m²), HD 285968 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 285968 is classified as a low-mass red dwarf of spectral type M2 V with an effective photospheric temperature of 3,703 K, a radius of 0.4782 R☉, a mass of 0.5 M☉, an estimated bolometric luminosity of 0.039 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.62 Gyr and a metallicity of [Fe/H] = -0.1 dex (near-solar heavy-element abundance). From Earth, HD 285968 shines at apparent V-band magnitude 9.95 (accessible to binoculars and small amateur telescopes) in the Northern 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 285968 |
| Spectral Type | M2 V |
| Effective Temp (Teff) | 3,703 K |
| Stellar Radius | 0.4782 R☉ |
| Stellar Mass | 0.5000 M☉ |
| Bolometric Luminosity | 0.039 L☉ |
| Metallicity [Fe/H] | -0.100 dex |
| Stellar Age | 3.620 Gyr |
| Apparent Magnitude | V: 9.950 · G: 9.000 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.066000 AU |
| Orbital Period | 8.784 days |
| Mean Orbital Velocity | 81.7 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 2.04 g/cm³ (19.3 km/s vesc) |
| Insolation Flux | 5.0456 S⊕ (~6,867 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 30.900 LY (9.470 pc) |