55 Cnc d
Astrophysical Synthesis & Habitability Characterization
55 Cnc d is a confirmed gas giant exoplanet orbiting the star 55 Cnc, located approximately 41 light-years (12.59 parsecs) from the Solar System. First announced in 2002 by Lick Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13 Earth radii (1.16 Jupiter radii) and has a measured mass of 1232.493 Earth masses (3.88 Jupiter masses). Combining its mass and radius yields a mean bulk density of 3.09 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 7.29 g⊕ (71.49 m/s²), and an escape velocity of 108.9 km/s.
In its orbital architecture around 55 Cnc, 55 Cnc d completes one full revolution every 4799 Earth days (13.14Julian years) at a semi-major axis of 5.6 AU (a wide outer-system orbit beyond Jupiter's 5.20 AU distance in our Solar System). Its mean orbital velocity is approximately 12.7 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.0913 carries the world between 5.0887 AU at periapsis and 6.1113 AU at apoapsis, driving measurable seasonal insolation cycles.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 105 K (-168°C / -270°F) and an incident flux of 0.02 S⊕ (~28 W/m²), surface water and volatile species on 55 Cnc d would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star 55 Cnc is classified as a solar-type yellow star of spectral type G8 V with an effective photospheric temperature of 5,198 K, a radius of 0.98 R☉, a mass of 1.015 M☉, an estimated bolometric luminosity of 0.629 L☉. Stellar evolution modeling indicates an estimated stellar age of 10 Gyr and a metallicity of [Fe/H] = 0.39 dex (metal-rich relative to the Sun). From Earth, 55 Cnc shines at apparent V-band magnitude 5.951 (visible to the unaided human eye under dark skies) in the Northern celestial hemisphere. The 55 Cnc system is a multi-planet architecture hosting 5 confirmed worlds, with 55 Cnc d sharing its stellar neighborhood alongside 55 Cnc e, 55 Cnc b, 55 Cnc c, 55 Cnc f.
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: Lick Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | 55 Cnc |
| Spectral Type | G8 V |
| Effective Temp (Teff) | 5,198 K |
| Stellar Radius | 0.9800 R☉ |
| Stellar Mass | 1.0150 M☉ |
| Bolometric Luminosity | 0.629 L☉ |
| Metallicity [Fe/H] | 0.390 dex |
| Stellar Age | 10.000 Gyr |
| Apparent Magnitude | V: 5.951 · G: 5.730 |
| System Architecture | 2 Stars, 7 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 5.600000 AU |
| Orbital Period | 4799 days |
| Mean Orbital Velocity | 12.7 km/s |
| Orbital Eccentricity (e) | 0.09130 |
| Orbital Inclination (i) | 89.7300° |
| Mean Bulk Density | 3.09 g/cm³ (108.9 km/s vesc) |
| Insolation Flux | 0.0203 S⊕ (~28 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 41.000 LY (12.586 pc) |