Proxima Cen d
Astrophysical Synthesis & Habitability Characterization
Proxima Cen d is a confirmed sub-earth exoplanet orbiting the star Proxima Cen, located approximately 4.2 light-years (1.3 parsecs) from the Solar System. First announced in 2025 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 0.692 Earth radii and has a measured mass of 0.26 Earth masses. Combining its mass and radius yields a mean bulk density of 4.33 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 0.54 g⊕ (5.3 m/s²), and an escape velocity of 6.9 km/s.
In its orbital architecture around Proxima Cen, Proxima Cen d completes one full revolution every 5.123 Earth days at a semi-major axis of 0.02881 AU (an ultra-close orbit less than one-seventh of Mercury's 0.387 AU distance from the Sun, where strong stellar tidal forces typically induce synchronous rotation). Its mean orbital velocity is approximately 61.2 km/s (compared to Earth's 29.8 km/s). The orbit is modeled as circular (e = 0.00), maintaining a constant stellar distance throughout its year.
✓ Classified as a Temperate Habitable Zone Candidate.
With an estimated equilibrium temperature of 282 K (+9°C / +48°F) and an incident stellar irradiance of 1.81 S⊕ (~2,469 W/m²), Proxima Cen d orbits within the empirical circumstellar habitable zone where a rocky surface under sufficient atmospheric pressure can maintain liquid surface water.
The host star Proxima Cen is classified as a low-mass red dwarf of spectral type M5.5 V with an effective photospheric temperature of 2,900 K, a radius of 0.141 R☉, a mass of 0.1221 M☉, an estimated bolometric luminosity of 0.00126 L☉. From Earth, Proxima Cen shines at apparent V-band magnitude 11.01 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The Proxima Cen system is a multi-planet architecture hosting 2 confirmed worlds, with Proxima Cen d sharing its stellar neighborhood alongside Proxima Cen 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: La Silla Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | Proxima Cen |
| Spectral Type | M5.5 V |
| Effective Temp (Teff) | 2,900 K |
| Stellar Radius | 0.1410 R☉ |
| Stellar Mass | 0.1221 M☉ |
| Bolometric Luminosity | 0.00126 L☉ |
| Metallicity [Fe/H] | — |
| Stellar Age | — |
| Apparent Magnitude | V: 11.010 · G: 8.954 |
| System Architecture | 3 Stars, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.028810 AU |
| Orbital Period | 5.123 days |
| Mean Orbital Velocity | 61.2 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 4.33 g/cm³ (6.9 km/s vesc) |
| Insolation Flux | 1.8140 S⊕ (~2,469 W/m²) |
| Habitable Zone Status | ★ Temperate Zone |
| Celestial Distance | 4.200 LY (1.301 pc) |