HD 69830 d
Astrophysical Synthesis & Habitability Characterization
HD 69830 d is a confirmed sub-neptune exoplanet orbiting the star HD 69830, located approximately 41 light-years (12.56 parsecs) from the Solar System. First announced in 2006 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 4.45 Earth radii (0.4 Jupiter radii) and has a measured mass of 18.1 Earth masses. Combining its mass and radius yields a mean bulk density of 1.13 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.91 g⊕ (8.92 m/s²), and an escape velocity of 22.6 km/s.
In its orbital architecture around HD 69830, HD 69830 d completes one full revolution every 197 Earth days at a semi-major axis of 0.63 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 34.8 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.07 carries the world between 0.5859 AU at periapsis and 0.6741 AU at apoapsis, driving measurable seasonal insolation cycles.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 4.450 R⊕, HD 69830 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 HD 69830 is classified as an orange K-type star of spectral type K0V with an effective photospheric temperature of 5,385 K, a radius of 0.8869 R☉, a mass of 0.86 M☉, an estimated bolometric luminosity of 0.593 L☉. Stellar evolution modeling indicates an estimated stellar age of 7 Gyr and a metallicity of [Fe/H] = -0.05 dex (near-solar heavy-element abundance). From Earth, HD 69830 shines at apparent V-band magnitude 5.96 (visible to the unaided human eye under dark skies) in the Southern celestial hemisphere. The HD 69830 system is a multi-planet architecture hosting 3 confirmed worlds, with HD 69830 d sharing its stellar neighborhood alongside HD 69830 b, HD 69830 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 69830 |
| Spectral Type | K0V |
| Effective Temp (Teff) | 5,385 K |
| Stellar Radius | 0.8869 R☉ |
| Stellar Mass | 0.8600 M☉ |
| Bolometric Luminosity | 0.593 L☉ |
| Metallicity [Fe/H] | -0.050 dex |
| Stellar Age | 7.000 Gyr |
| Apparent Magnitude | V: 5.960 · G: 5.754 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.630000 AU |
| Orbital Period | 197 days |
| Mean Orbital Velocity | 34.8 km/s |
| Orbital Eccentricity (e) | 0.07000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.13 g/cm³ (22.6 km/s vesc) |
| Insolation Flux | 1.5182 S⊕ (~2,066 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 41.000 LY (12.559 pc) |