GJ 849 c
Astrophysical Synthesis & Habitability Characterization
GJ 849 c is a confirmed gas giant exoplanet orbiting the star GJ 849, located approximately 28.7 light-years (8.8 parsecs) from the Solar System. First announced in 2014 by W. M. Keck Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13.8 Earth radii (1.23 Jupiter radii) and has a measured mass of 314.65 Earth masses (0.99 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.66 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.65 g⊕ (16.18 m/s²), and an escape velocity of 53.4 km/s.
In its orbital architecture around GJ 849, GJ 849 c completes one full revolution every 5990 Earth days (16.4Julian years) at a semi-major axis of 4.95 AU (corresponding to the middle-system regime between Mars at 1.52 AU and Jupiter at 5.20 AU). Its mean orbital velocity is approximately 9 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.092 carries the world between 4.4946 AU at periapsis and 5.4054 AU at apoapsis, driving measurable seasonal insolation cycles.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 50 K (-223°C / -369°F) and an incident flux of 0.00 S⊕ (~1 W/m²), surface water and volatile species on GJ 849 c would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star GJ 849 is classified as a low-mass red dwarf of spectral type M3.5 with an effective photospheric temperature of 3,467 K, a radius of 0.45 R☉, a mass of 0.45 M☉, an estimated bolometric luminosity of 0.026 L☉. Stellar evolution modeling indicates an estimated stellar age of 3 Gyr and a metallicity of [Fe/H] = 0.09 dex (metal-rich relative to the Sun). From Earth, GJ 849 shines at apparent V-band magnitude 10.41 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The GJ 849 system is a multi-planet architecture hosting 2 confirmed worlds, with GJ 849 c sharing its stellar neighborhood alongside GJ 849 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: W. M. Keck Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | GJ 849 |
| Spectral Type | M3.5 |
| Effective Temp (Teff) | 3,467 K |
| Stellar Radius | 0.4500 R☉ |
| Stellar Mass | 0.4500 M☉ |
| Bolometric Luminosity | 0.026 L☉ |
| Metallicity [Fe/H] | 0.090 dex |
| Stellar Age | 3.000 Gyr |
| Apparent Magnitude | V: 10.410 · G: 9.225 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 4.950000 AU |
| Orbital Period | 5990 days |
| Mean Orbital Velocity | 9 km/s |
| Orbital Eccentricity (e) | 0.09200 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.66 g/cm³ (53.4 km/s vesc) |
| Insolation Flux | 0.0010 S⊕ (~1 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 28.700 LY (8.801 pc) |