G 261-6 b
Astrophysical Synthesis & Habitability Characterization
G 261-6 b is a confirmed terrestrial exoplanet orbiting the star G 261-6, located approximately 34.7 light-years (10.63 parsecs) from the Solar System. First announced in 2025 by Calar Alto Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 1.1 Earth radii and has a measured mass of 1.37 Earth masses. Combining its mass and radius yields a mean bulk density of 5.68 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.13 g⊕ (11.08 m/s²), and an escape velocity of 12.5 km/s.
In its orbital architecture around G 261-6, G 261-6 b completes one full revolution every 5.454 Earth days at a semi-major axis of 0.02971 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 59.3 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 322 K (+49°C / +120°F) and an incident stellar irradiance of 1.80 S⊕ (~2,450 W/m²), G 261-6 b orbits within the empirical circumstellar habitable zone where a rocky surface under sufficient atmospheric pressure can maintain liquid surface water.
The host star G 261-6 is classified as a low-mass red dwarf of spectral type M5.5 V with an effective photospheric temperature of 2,907 K, a radius of 0.1532 R☉, a mass of 0.118 M☉, an estimated bolometric luminosity of 0.00150 L☉. From Earth, G 261-6 shines at apparent V-band magnitude 15.75 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.
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: Calar Alto Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | G 261-6 |
| Spectral Type | M5.5 V |
| Effective Temp (Teff) | 2,907 K |
| Stellar Radius | 0.1532 R☉ |
| Stellar Mass | 0.1180 M☉ |
| Bolometric Luminosity | 0.00150 L☉ |
| Metallicity [Fe/H] | — |
| Stellar Age | — |
| Apparent Magnitude | V: 15.750 · G: 13.404 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.029710 AU |
| Orbital Period | 5.454 days |
| Mean Orbital Velocity | 59.3 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 5.68 g/cm³ (12.5 km/s vesc) |
| Insolation Flux | 1.8000 S⊕ (~2,450 W/m²) |
| Habitable Zone Status | ★ Temperate Zone |
| Celestial Distance | 34.700 LY (10.627 pc) |