HD 63433 c
Astrophysical Synthesis & Habitability Characterization
HD 63433 c is a confirmed sub-neptune exoplanet orbiting the star HD 63433, located approximately 73.1 light-years (22.4 parsecs) from the Solar System. First announced in 2020 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.0698% across the stellar disk), this world measures 2.692 Earth radii and has a measured mass of 15.539 Earth masses. Combining its mass and radius yields a mean bulk density of 4.39 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 2.14 g⊕ (20.99 m/s²), and an escape velocity of 26.9 km/s.
In its orbital architecture around HD 63433, HD 63433 c completes one full revolution every 20.544 Earth days at a semi-major axis of 0.146 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 77.3 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.21 carries the world between 0.1153 AU at periapsis and 0.1767 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 679 K (+406°C / +763°F) and receiving 35.36 S⊕ (~48,123 W/m²), HD 63433 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 63433 is classified as a solar-type yellow star of spectral type G5 V with an effective photospheric temperature of 5,553 K, a radius of 0.934 R☉, a mass of 0.956 M☉, an estimated bolometric luminosity of 0.744 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.414 Gyr and a metallicity of [Fe/H] = -0.07 dex (near-solar heavy-element abundance). From Earth, HD 63433 shines at apparent V-band magnitude 6.92 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The HD 63433 system is a multi-planet architecture hosting 3 confirmed worlds, with HD 63433 c sharing its stellar neighborhood alongside HD 63433 d, HD 63433 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: Transiting Exoplanet Survey Satellite (TESS) · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 63433 |
| Spectral Type | G5 V |
| Effective Temp (Teff) | 5,553 K |
| Stellar Radius | 0.9340 R☉ |
| Stellar Mass | 0.9560 M☉ |
| Bolometric Luminosity | 0.744 L☉ |
| Metallicity [Fe/H] | -0.070 dex |
| Stellar Age | 0.414 Gyr |
| Apparent Magnitude | V: 6.920 · G: 6.718 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.146000 AU |
| Orbital Period | 20.544 days |
| Mean Orbital Velocity | 77.3 km/s |
| Orbital Eccentricity (e) | 0.21000 |
| Orbital Inclination (i) | 89.0700° |
| Mean Bulk Density | 4.39 g/cm³ (26.9 km/s vesc) |
| Insolation Flux | 35.3582 S⊕ (~48,123 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 73.100 LY (22.404 pc) |