75 Cet c
Astrophysical Synthesis & Habitability Characterization
75 Cet c is a confirmed gas giant exoplanet orbiting the star 75 Cet, located approximately 270.6 light-years (82.96 parsecs) from the Solar System. First announced in 2023 by Okayama Astrophysical Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13.9 Earth radii (1.24 Jupiter radii) and has a measured mass of 289.86 Earth masses (0.91 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.6 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.5 g⊕ (14.71 m/s²), and an escape velocity of 51.1 km/s.
In its orbital architecture around 75 Cet, 75 Cet c completes one full revolution every 2051.62 Earth days (5.62Julian years) at a semi-major axis of 3.929 AU (corresponding to the middle-system regime between Mars at 1.52 AU and Jupiter at 5.20 AU). Its mean orbital velocity is approximately 20.8 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.023 (ranging from 3.8386 AU at periapsis to 4.0194 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 377 K (+104°C / +219°F) and receiving 3.36 S⊕ (~4,569 W/m²), 75 Cet c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star 75 Cet is classified as a solar-type yellow star of spectral type G3 III with an effective photospheric temperature of 4,809 K, a radius of 10.38 R☉, a mass of 1.92 M☉, an estimated bolometric luminosity of 51.702 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.1 dex (metal-rich relative to the Sun). From Earth, 75 Cet shines at apparent V-band magnitude 5.353 (visible to the unaided human eye under dark skies) in the Southern celestial hemisphere. The 75 Cet system is a multi-planet architecture hosting 2 confirmed worlds, with 75 Cet c sharing its stellar neighborhood alongside 75 Cet b.
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: Okayama Astrophysical Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | 75 Cet |
| Spectral Type | G3 III |
| Effective Temp (Teff) | 4,809 K |
| Stellar Radius | 10.3800 R☉ |
| Stellar Mass | 1.9200 M☉ |
| Bolometric Luminosity | 51.702 L☉ |
| Metallicity [Fe/H] | 0.100 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 5.353 · G: 5.093 |
| System Architecture | 2 Stars, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 3.929000 AU |
| Orbital Period | 2051.62 days |
| Mean Orbital Velocity | 20.8 km/s |
| Orbital Eccentricity (e) | 0.02300 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.6 g/cm³ (51.1 km/s vesc) |
| Insolation Flux | 3.3569 S⊕ (~4,569 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 270.600 LY (82.961 pc) |