eps Tau b
Astrophysical Synthesis & Habitability Characterization
eps Tau b is a confirmed gas giant exoplanet orbiting the star eps Tau, located approximately 155 light-years (47.53 parsecs) from the Solar System. First announced in 2006 by Okayama Astrophysical Observatory 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 2285.186 Earth masses (7.19 Jupiter masses). Combining its mass and radius yields a mean bulk density of 6.15 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 14.17 g⊕ (138.96 m/s²), and an escape velocity of 150 km/s.
In its orbital architecture around eps Tau, eps Tau b completes one full revolution every 585.82 Earth days (1.6Julian years) at a semi-major axis of 1.878 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 34.9 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.076 carries the world between 1.7353 AU at periapsis and 2.0207 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 603 K (+330°C / +626°F) and receiving 22.15 S⊕ (~30,142 W/m²), eps Tau b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star eps Tau is classified as an orange K-type star of spectral type K0 III with an effective photospheric temperature of 4,877 K, a radius of 12.35 R☉, a mass of 2.57 M☉, an estimated bolometric luminosity of 77.417 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.1 dex (metal-rich relative to the Sun). From Earth, eps Tau shines at apparent V-band magnitude 3.523 (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: Okayama Astrophysical Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | eps Tau |
| Spectral Type | K0 III |
| Effective Temp (Teff) | 4,877 K |
| Stellar Radius | 12.3500 R☉ |
| Stellar Mass | 2.5700 M☉ |
| Bolometric Luminosity | 77.417 L☉ |
| Metallicity [Fe/H] | 0.100 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 3.523 · G: 3.273 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.878000 AU |
| Orbital Period | 585.82 days |
| Mean Orbital Velocity | 34.9 km/s |
| Orbital Eccentricity (e) | 0.07600 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 6.15 g/cm³ (150 km/s vesc) |
| Insolation Flux | 22.1470 S⊕ (~30,142 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 155.000 LY (47.529 pc) |