GJ 273 b
Astrophysical Synthesis & Habitability Characterization
GJ 273 b is a confirmed super-earth exoplanet orbiting the star GJ 273, located approximately 19.3 light-years (5.92 parsecs) from the Solar System. First announced in 2017 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 1.51 Earth radii and has a measured mass of 2.89 Earth masses. Combining its mass and radius yields a mean bulk density of 4.63 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.27 g⊕ (12.45 m/s²), and an escape velocity of 15.5 km/s.
In its orbital architecture around GJ 273, GJ 273 b completes one full revolution every 18.65 Earth days at a semi-major axis of 0.091101 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 53.1 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.1 carries the world between 0.082 AU at periapsis and 0.1002 AU at apoapsis, driving measurable seasonal insolation cycles.
✓ Classified as a Temperate Habitable Zone Candidate.
With an estimated equilibrium temperature of 292 K (+19°C / +66°F) and an incident stellar irradiance of 1.06 S⊕ (~1,443 W/m²), GJ 273 b orbits within the empirical circumstellar habitable zone where a rocky surface under sufficient atmospheric pressure can maintain liquid surface water.
The host star GJ 273 is classified as a low-mass red dwarf of spectral type M3.5 with an effective photospheric temperature of 3,382 K, a radius of 0.293 R☉, a mass of 0.29 M☉, an estimated bolometric luminosity of 0.01 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.09 dex (metal-rich relative to the Sun). From Earth, GJ 273 shines at apparent V-band magnitude 9.84 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The GJ 273 system is a multi-planet architecture hosting 2 confirmed worlds, with GJ 273 b sharing its stellar neighborhood alongside GJ 273 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: La Silla Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | GJ 273 |
| Spectral Type | M3.5 |
| Effective Temp (Teff) | 3,382 K |
| Stellar Radius | 0.2930 R☉ |
| Stellar Mass | 0.2900 M☉ |
| Bolometric Luminosity | 0.01 L☉ |
| Metallicity [Fe/H] | 0.090 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 9.840 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.091101 AU |
| Orbital Period | 18.65 days |
| Mean Orbital Velocity | 53.1 km/s |
| Orbital Eccentricity (e) | 0.10000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 4.63 g/cm³ (15.5 km/s vesc) |
| Insolation Flux | 1.0600 S⊕ (~1,443 W/m²) |
| Habitable Zone Status | ★ Temperate Zone |
| Celestial Distance | 19.300 LY (5.922 pc) |