HD 48948 d
Astrophysical Synthesis & Habitability Characterization
HD 48948 d is a confirmed sub-neptune exoplanet orbiting the star HD 48948, located approximately 55.1 light-years (16.9 parsecs) from the Solar System. First announced in 2024 by Roque de los Muchachos Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 3.24 Earth radii (0.29 Jupiter radii) and has a measured mass of 10.59 Earth masses. Combining its mass and radius yields a mean bulk density of 1.72 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.01 g⊕ (9.9 m/s²), and an escape velocity of 20.2 km/s.
In its orbital architecture around HD 48948, HD 48948 d completes one full revolution every 151.92 Earth days at a semi-major axis of 0.4894 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 35 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.055 carries the world between 0.4625 AU at periapsis and 0.5163 AU at apoapsis, driving measurable seasonal insolation cycles.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 3.240 R⊕, HD 48948 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 48948 is classified as an orange K-type star of spectral type K3 V with an effective photospheric temperature of 4,593 K, a radius of 0.679 R☉, a mass of 0.686 M☉, an estimated bolometric luminosity of 0.184 L☉. Stellar evolution modeling indicates an estimated stellar age of 11.48 Gyr and a metallicity of [Fe/H] = -0.21 dex (metal-poor relative to the Sun). From Earth, HD 48948 shines at apparent V-band magnitude 8.58 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The HD 48948 system is a multi-planet architecture hosting 3 confirmed worlds, with HD 48948 d sharing its stellar neighborhood alongside HD 48948 b, HD 48948 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: Roque de los Muchachos Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 48948 |
| Spectral Type | K3 V |
| Effective Temp (Teff) | 4,593 K |
| Stellar Radius | 0.6790 R☉ |
| Stellar Mass | 0.6860 M☉ |
| Bolometric Luminosity | 0.184 L☉ |
| Metallicity [Fe/H] | -0.210 dex |
| Stellar Age | 11.480 Gyr |
| Apparent Magnitude | V: 8.580 · G: 8.113 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.489400 AU |
| Orbital Period | 151.92 days |
| Mean Orbital Velocity | 35 km/s |
| Orbital Eccentricity (e) | 0.05500 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.72 g/cm³ (20.2 km/s vesc) |
| Insolation Flux | 2.4600 S⊕ (~3,348 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 55.100 LY (16.904 pc) |