HD 63433 d
Astrophysical Synthesis & Habitability Characterization
HD 63433 d is a confirmed terrestrial exoplanet orbiting the star HD 63433, located approximately 73.1 light-years (22.4 parsecs) from the Solar System. First announced in 2023 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.0116% across the stellar disk), this world measures 1.073 Earth radii and has a measured mass of 1.25 Earth masses. Combining its mass and radius yields a mean bulk density of 5.58 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.09 g⊕ (10.69 m/s²), and an escape velocity of 12.1 km/s.
In its orbital architecture around HD 63433, HD 63433 d completes one full revolution every 4.209 Earth days at a semi-major axis of 0.0503 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 130 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.16 carries the world between 0.0423 AU at periapsis and 0.0583 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1040 K (+767°C / +1413°F) and receiving 296.43 S⊕ (~403,444 W/m²), HD 63433 d 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 5,688 K, a radius of 0.912 R☉, a mass of 0.99 M☉, an estimated bolometric luminosity of 0.781 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.414 Gyr and a metallicity of [Fe/H] = 0.03 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 d sharing its stellar neighborhood alongside HD 63433 b, HD 63433 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: 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) | 5,688 K |
| Stellar Radius | 0.9120 R☉ |
| Stellar Mass | 0.9900 M☉ |
| Bolometric Luminosity | 0.781 L☉ |
| Metallicity [Fe/H] | 0.030 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) | 0.050300 AU |
| Orbital Period | 4.209 days |
| Mean Orbital Velocity | 130 km/s |
| Orbital Eccentricity (e) | 0.16000 |
| Orbital Inclination (i) | 88.7300° |
| Mean Bulk Density | 5.58 g/cm³ (12.1 km/s vesc) |
| Insolation Flux | 296.4321 S⊕ (~403,444 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 73.100 LY (22.404 pc) |