GJ 433 d
Astrophysical Synthesis & Habitability Characterization
GJ 433 d is a confirmed sub-neptune exoplanet orbiting the star GJ 433, located approximately 29.6 light-years (9.07 parsecs) from the Solar System. First announced in 2020 by Multiple Facilities using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 2.14 Earth radii and has a measured mass of 5.223 Earth masses. Combining its mass and radius yields a mean bulk density of 2.94 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.14 g⊕ (11.18 m/s²), and an escape velocity of 17.5 km/s.
In its orbital architecture around GJ 433, GJ 433 d completes one full revolution every 36.059 Earth days at a semi-major axis of 0.178 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 53.7 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.07 carries the world between 0.1655 AU at periapsis and 0.1905 AU at apoapsis, driving measurable seasonal insolation cycles.
✓ Classified as a Temperate Habitable Zone Candidate.
With an estimated equilibrium temperature of 280 K (+7°C / +45°F) and an incident stellar irradiance of 0.63 S⊕ (~859 W/m²), GJ 433 d orbits within the empirical circumstellar habitable zone where a rocky surface under sufficient atmospheric pressure can maintain liquid surface water.
The host star GJ 433 is classified as a low-mass red dwarf of spectral type M2V with an effective photospheric temperature of 3,461 K, a radius of 0.5 R☉, a mass of 0.48 M☉, an estimated bolometric luminosity of 0.032 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.17 dex (metal-poor relative to the Sun). From Earth, GJ 433 shines at apparent V-band magnitude 9.81 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere. The GJ 433 system is a multi-planet architecture hosting 3 confirmed worlds, with GJ 433 d sharing its stellar neighborhood alongside GJ 433 b, GJ 433 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: Multiple Facilities · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | GJ 433 |
| Spectral Type | M2V |
| Effective Temp (Teff) | 3,461 K |
| Stellar Radius | 0.5000 R☉ |
| Stellar Mass | 0.4800 M☉ |
| Bolometric Luminosity | 0.032 L☉ |
| Metallicity [Fe/H] | -0.170 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 9.810 · G: 8.891 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.178000 AU |
| Orbital Period | 36.059 days |
| Mean Orbital Velocity | 53.7 km/s |
| Orbital Eccentricity (e) | 0.07000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 2.94 g/cm³ (17.5 km/s vesc) |
| Insolation Flux | 0.6312 S⊕ (~859 W/m²) |
| Habitable Zone Status | ★ Temperate Zone |
| Celestial Distance | 29.600 LY (9.065 pc) |