tau Cet f
Astrophysical Synthesis & Habitability Characterization
tau Cet f is a confirmed super-earth exoplanet orbiting the star tau Cet, located approximately 11.8 light-years (3.6 parsecs) from the Solar System. First announced in 2017 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 1.81 Earth radii and has a measured mass of 3.93 Earth masses. Combining its mass and radius yields a mean bulk density of 3.65 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.2 g⊕ (11.77 m/s²), and an escape velocity of 16.5 km/s.
In its orbital architecture around tau Cet, tau Cet f completes one full revolution every 636.13 Earth days (1.74Julian years) at a semi-major axis of 1.334 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 22.8 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.16 carries the world between 1.1206 AU at periapsis and 1.5474 AU at apoapsis, driving measurable seasonal insolation cycles.
✓ Classified as a Temperate Habitable Zone Candidate.
With an estimated equilibrium temperature of 202 K (-71°C / -96°F) and an incident stellar irradiance of 0.28 S⊕ (~379 W/m²), tau Cet f orbits within the empirical circumstellar habitable zone where a rocky surface under sufficient atmospheric pressure can maintain liquid surface water.
The host star tau Cet is classified as a solar-type yellow star of spectral type G8.5V with an effective photospheric temperature of 5,310 K, a radius of 0.83 R☉, a mass of 0.783 M☉, an estimated bolometric luminosity of 0.491 L☉. Stellar evolution modeling indicates an estimated stellar age of 12.12 Gyr and a metallicity of [Fe/H] = -0.52 dex (metal-poor relative to the Sun). From Earth, tau Cet shines at apparent V-band magnitude 3.496 (visible to the unaided human eye under dark skies) in the Southern celestial hemisphere. The tau Cet system is a multi-planet architecture hosting 3 confirmed worlds, with tau Cet f sharing its stellar neighborhood alongside tau Cet g, tau Cet h.
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 | tau Cet |
| Spectral Type | G8.5V |
| Effective Temp (Teff) | 5,310 K |
| Stellar Radius | 0.8300 R☉ |
| Stellar Mass | 0.7830 M☉ |
| Bolometric Luminosity | 0.491 L☉ |
| Metallicity [Fe/H] | -0.520 dex |
| Stellar Age | 12.120 Gyr |
| Apparent Magnitude | V: 3.496 · G: 3.249 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.334000 AU |
| Orbital Period | 636.13 days |
| Mean Orbital Velocity | 22.8 km/s |
| Orbital Eccentricity (e) | 0.16000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 3.65 g/cm³ (16.5 km/s vesc) |
| Insolation Flux | 0.2782 S⊕ (~379 W/m²) |
| Habitable Zone Status | ★ Temperate Zone |
| Celestial Distance | 11.800 LY (3.603 pc) |