HD 86226 c
Astrophysical Synthesis & Habitability Characterization
HD 86226 c is a confirmed sub-neptune exoplanet orbiting the star HD 86226, located approximately 149 light-years (45.68 parsecs) from the Solar System. First announced in 2020 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.0354% across the stellar disk), this world measures 2.16 Earth radii and has a measured mass of 7.25 Earth masses. Combining its mass and radius yields a mean bulk density of 3.97 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.55 g⊕ (15.2 m/s²), and an escape velocity of 20.5 km/s.
In its orbital architecture around HD 86226, HD 86226 c completes one full revolution every 3.984 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 133.8 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.075 carries the world between 0.0453 AU at periapsis and 0.0527 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1311 K (+1038°C / +1900°F) and receiving 647.90 S⊕ (~881,793 W/m²), HD 86226 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HD 86226 is classified as a solar-type yellow star of spectral type G1 V with an effective photospheric temperature of 5,863 K, a radius of 1.053 R☉, a mass of 1.019 M☉, an estimated bolometric luminosity of 1.176 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.6 Gyr and a metallicity of [Fe/H] = 0.018 dex (near-solar heavy-element abundance). From Earth, HD 86226 shines at apparent V-band magnitude 7.93 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere. The HD 86226 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 86226 c sharing its stellar neighborhood alongside HD 86226 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 86226 |
| Spectral Type | G1 V |
| Effective Temp (Teff) | 5,863 K |
| Stellar Radius | 1.0530 R☉ |
| Stellar Mass | 1.0190 M☉ |
| Bolometric Luminosity | 1.176 L☉ |
| Metallicity [Fe/H] | 0.018 dex |
| Stellar Age | 4.600 Gyr |
| Apparent Magnitude | V: 7.930 · G: 7.771 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.049000 AU |
| Orbital Period | 3.984 days |
| Mean Orbital Velocity | 133.8 km/s |
| Orbital Eccentricity (e) | 0.07500 |
| Orbital Inclination (i) | 86.4500° |
| Mean Bulk Density | 3.97 g/cm³ (20.5 km/s vesc) |
| Insolation Flux | 647.9010 S⊕ (~881,793 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 149.000 LY (45.683 pc) |