HD 2685 b
Astrophysical Synthesis & Habitability Characterization
HD 2685 b is a confirmed gas giant exoplanet orbiting the star HD 2685, located approximately 642 light-years (196.85 parsecs) from the Solar System. First announced in 2019 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.8998% across the stellar disk), this world measures 16.141 Earth radii (1.44 Jupiter radii) and has a measured mass of 371.861 Earth masses (1.17 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.49 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.43 g⊕ (14.02 m/s²), and an escape velocity of 53.7 km/s.
In its orbital architecture around HD 2685, HD 2685 b completes one full revolution every 4.127 Earth days at a semi-major axis of 0.0568 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 149.7 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.091 carries the world between 0.0516 AU at periapsis and 0.062 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 2061 K (+1788°C / +3250°F) and receiving 1,436.49 S⊕ (~1,955,063 W/m²), HD 2685 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 2685 is classified as a stellar host with an effective photospheric temperature of 6,801 K, a radius of 1.56 R☉, a mass of 1.43 M☉, an estimated bolometric luminosity of 4.671 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.31 Gyr and a metallicity of [Fe/H] = 0.02 dex (near-solar heavy-element abundance). From Earth, HD 2685 shines at apparent V-band magnitude 9.595 (accessible to binoculars and small amateur telescopes) in the Southern 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: Transiting Exoplanet Survey Satellite (TESS) · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 2685 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,801 K |
| Stellar Radius | 1.5600 R☉ |
| Stellar Mass | 1.4300 M☉ |
| Bolometric Luminosity | 4.671 L☉ |
| Metallicity [Fe/H] | 0.020 dex |
| Stellar Age | 1.310 Gyr |
| Apparent Magnitude | V: 9.595 · G: 9.520 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.056800 AU |
| Orbital Period | 4.127 days |
| Mean Orbital Velocity | 149.7 km/s |
| Orbital Eccentricity (e) | 0.09100 |
| Orbital Inclination (i) | 89.2520° |
| Mean Bulk Density | 0.49 g/cm³ (53.7 km/s vesc) |
| Insolation Flux | 1436.4900 S⊕ (~1,955,063 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 642.000 LY (196.852 pc) |