HD 221416 b
Astrophysical Synthesis & Habitability Characterization
HD 221416 b is a confirmed gas giant exoplanet orbiting the star HD 221416, located approximately 311.6 light-years (95.55 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 0.0816% across the stellar disk), this world measures 9.17 Earth radii (0.82 Jupiter radii) and has a measured mass of 60.5 Earth masses (0.19 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.43 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.72 g⊕ (7.06 m/s²), and an escape velocity of 28.7 km/s.
In its orbital architecture around HD 221416, HD 221416 b completes one full revolution every 14.277 Earth days at a semi-major axis of 0.1228 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 93.6 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.115 carries the world between 0.1087 AU at periapsis and 0.1369 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1315 K (+1042°C / +1908°F) and receiving 495.91 S⊕ (~674,929 W/m²), HD 221416 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 221416 is classified as an orange K-type star of spectral type K0 IV/V with an effective photospheric temperature of 5,080 K, a radius of 2.943 R☉, a mass of 1.212 M☉, an estimated bolometric luminosity of 5.175 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.9 Gyr and a metallicity of [Fe/H] = -0.08 dex (near-solar heavy-element abundance). From Earth, HD 221416 shines at apparent V-band magnitude 8.15 (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 221416 |
| Spectral Type | K0 IV/V |
| Effective Temp (Teff) | 5,080 K |
| Stellar Radius | 2.9430 R☉ |
| Stellar Mass | 1.2120 M☉ |
| Bolometric Luminosity | 5.175 L☉ |
| Metallicity [Fe/H] | -0.080 dex |
| Stellar Age | 4.900 Gyr |
| Apparent Magnitude | V: 8.150 · G: 7.908 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.122800 AU |
| Orbital Period | 14.277 days |
| Mean Orbital Velocity | 93.6 km/s |
| Orbital Eccentricity (e) | 0.11500 |
| Orbital Inclination (i) | 85.7500° |
| Mean Bulk Density | 0.43 g/cm³ (28.7 km/s vesc) |
| Insolation Flux | 495.9065 S⊕ (~674,929 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 311.600 LY (95.548 pc) |