alf Tau b
Astrophysical Synthesis & Habitability Characterization
alf Tau b is a confirmed gas giant exoplanet orbiting the star alf Tau, located approximately 66.6 light-years (20.43 parsecs) from the Solar System. First announced in 2015 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.7 Earth radii (1.13 Jupiter radii) and has a measured mass of 2056.36 Earth masses (6.47 Jupiter masses). Combining its mass and radius yields a mean bulk density of 5.54 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 12.75 g⊕ (125.03 m/s²), and an escape velocity of 142.3 km/s.
In its orbital architecture around alf Tau, alf Tau b completes one full revolution every 628.96 Earth days (1.72Julian years) at a semi-major axis of 1.46 AU (comparable to the inner terrestrial zone between Venus, Earth at 1.00 AU, and Mars at 1.52 AU). Its mean orbital velocity is approximately 25.3 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.1 carries the world between 1.314 AU at periapsis and 1.606 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1087 K (+814°C / +1497°F) and receiving 220.44 S⊕ (~300,022 W/m²), alf Tau b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star alf Tau is classified as an orange K-type star of spectral type K5 III with an effective photospheric temperature of 4,055 K, a radius of 45.1 R☉, a mass of 1.13 M☉, an estimated bolometric luminosity of 493.408 L☉. Stellar evolution modeling indicates an estimated stellar age of 6.6 Gyr and a metallicity of [Fe/H] = -0.27 dex (metal-poor relative to the Sun). From Earth, alf Tau shines at apparent V-band magnitude 0.872 (visible to the unaided human eye under dark skies) 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: Multiple Observatories · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | alf Tau |
| Spectral Type | K5 III |
| Effective Temp (Teff) | 4,055 K |
| Stellar Radius | 45.1000 R☉ |
| Stellar Mass | 1.1300 M☉ |
| Bolometric Luminosity | 493.408 L☉ |
| Metallicity [Fe/H] | -0.270 dex |
| Stellar Age | 6.600 Gyr |
| Apparent Magnitude | V: 0.872 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.460000 AU |
| Orbital Period | 628.96 days |
| Mean Orbital Velocity | 25.3 km/s |
| Orbital Eccentricity (e) | 0.10000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 5.54 g/cm³ (142.3 km/s vesc) |
| Insolation Flux | 220.4420 S⊕ (~300,022 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 66.600 LY (20.433 pc) |