tau Boo b
Astrophysical Synthesis & Habitability Characterization
tau Boo b is a confirmed gas giant exoplanet orbiting the star tau Boo, located approximately 51.1 light-years (15.65 parsecs) from the Solar System. First announced in 1996 by Lick Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.8 Earth radii (1.14 Jupiter radii) and has a measured mass of 1891 Earth masses (5.95 Jupiter masses). Combining its mass and radius yields a mean bulk density of 4.97 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 11.54 g⊕ (113.17 m/s²), and an escape velocity of 136 km/s.
In its orbital architecture around tau Boo, tau Boo b completes one full revolution every 3.312 Earth days at a semi-major axis of 0.049 AU (an ultra-close orbit less than one-seventh of Mercury's 0.387 AU distance from the Sun, where strong stellar tidal forces typically induce synchronous rotation). Its mean orbital velocity is approximately 160.9 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.011 (ranging from 0.0485 AU at periapsis to 0.0495 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1682 K (+1409°C / +2568°F) and receiving 1,333.78 S⊕ (~1,815,278 W/m²), tau Boo b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star tau Boo is classified as a warm F-type star of spectral type F7 V with an effective photospheric temperature of 6,466 K, a radius of 1.4259 R☉, a mass of 1.32 M☉, an estimated bolometric luminosity of 3.189 L☉. Stellar evolution modeling indicates an estimated stellar age of 2 Gyr and a metallicity of [Fe/H] = 0.264 dex (metal-rich relative to the Sun). From Earth, tau Boo shines at apparent V-band magnitude 4.486 (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: Lick Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | tau Boo |
| Spectral Type | F7 V |
| Effective Temp (Teff) | 6,466 K |
| Stellar Radius | 1.4259 R☉ |
| Stellar Mass | 1.3200 M☉ |
| Bolometric Luminosity | 3.189 L☉ |
| Metallicity [Fe/H] | 0.264 dex |
| Stellar Age | 2.000 Gyr |
| Apparent Magnitude | V: 4.486 · G: 4.366 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.049000 AU |
| Orbital Period | 3.312 days |
| Mean Orbital Velocity | 160.9 km/s |
| Orbital Eccentricity (e) | 0.01100 |
| Orbital Inclination (i) | 44.5000° |
| Mean Bulk Density | 4.97 g/cm³ (136 km/s vesc) |
| Insolation Flux | 1333.7826 S⊕ (~1,815,278 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 51.100 LY (15.652 pc) |