pi Men c
Astrophysical Synthesis & Habitability Characterization
pi Men c is a confirmed sub-neptune exoplanet orbiting the star HD 39091, located approximately 59.6 light-years (18.27 parsecs) from the Solar System. First announced in 2018 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.025% across the stellar disk), this world measures 2.019 Earth radii and has a measured mass of 3.63 Earth masses. Combining its mass and radius yields a mean bulk density of 2.43 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 0.89 g⊕ (8.73 m/s²), and an escape velocity of 15 km/s.
In its orbital architecture around HD 39091, pi Men c completes one full revolution every 6.268 Earth days at a semi-major axis of 0.06839 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 118.7 km/s (compared to Earth's 29.8 km/s). The orbit is modeled as circular (e = 0.00), maintaining a constant stellar distance throughout its year.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1170 K (+897°C / +1647°F) and receiving 309.00 S⊕ (~420,549 W/m²), pi Men c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 39091 is classified as a solar-type yellow star of spectral type G0 V with an effective photospheric temperature of 5,998 K, a radius of 1.17 R☉, a mass of 1.07 M☉, an estimated bolometric luminosity of 1.59 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.98 Gyr and a metallicity of [Fe/H] = 0.09 dex (metal-rich relative to the Sun). From Earth, HD 39091 shines at apparent V-band magnitude 5.65 (visible to the unaided human eye under dark skies) in the Southern celestial hemisphere. The HD 39091 system is a multi-planet architecture hosting 3 confirmed worlds, with pi Men c sharing its stellar neighborhood alongside pi Men d, HD 39091 b.
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 39091 |
| Spectral Type | G0 V |
| Effective Temp (Teff) | 5,998 K |
| Stellar Radius | 1.1700 R☉ |
| Stellar Mass | 1.0700 M☉ |
| Bolometric Luminosity | 1.59 L☉ |
| Metallicity [Fe/H] | 0.090 dex |
| Stellar Age | 2.980 Gyr |
| Apparent Magnitude | V: 5.650 · G: 5.513 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.068390 AU |
| Orbital Period | 6.268 days |
| Mean Orbital Velocity | 118.7 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 87.0450° |
| Mean Bulk Density | 2.43 g/cm³ (15 km/s vesc) |
| Insolation Flux | 309.0000 S⊕ (~420,549 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 59.600 LY (18.270 pc) |