HD 85426 c
Astrophysical Synthesis & Habitability Characterization
HD 85426 c is a confirmed sub-neptune exoplanet orbiting the star TOI-1774, located approximately 176 light-years (53.97 parsecs) from the Solar System. First announced in 2026 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 3.19 Earth radii (0.28 Jupiter radii) and has a measured mass of 10.3 Earth masses. Combining its mass and radius yields a mean bulk density of 1.75 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.01 g⊕ (9.9 m/s²), and an escape velocity of 20.1 km/s.
In its orbital architecture around TOI-1774, HD 85426 c completes one full revolution every 35.73 Earth days. Its moderate orbital eccentricity of e = 0.06 driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 640 K (+367°C / +693°F), HD 85426 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-1774 is classified as a stellar host with an effective photospheric temperature of 5,746 K, a radius of 1.1303 R☉, a mass of 0.991 M☉, an estimated bolometric luminosity of 1.25 L☉. Stellar evolution modeling indicates an estimated stellar age of 7.4 Gyr and a metallicity of [Fe/H] = -0.02 dex (near-solar heavy-element abundance). From Earth, TOI-1774 shines at apparent V-band magnitude 8.25 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The TOI-1774 system is a multi-planet architecture hosting 2 confirmed worlds, with HD 85426 c sharing its stellar neighborhood alongside TOI-1774.01.
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 | TOI-1774 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,746 K |
| Stellar Radius | 1.1303 R☉ |
| Stellar Mass | 0.9910 M☉ |
| Bolometric Luminosity | 1.25 L☉ |
| Metallicity [Fe/H] | -0.020 dex |
| Stellar Age | 7.400 Gyr |
| Apparent Magnitude | V: 8.250 · G: 8.082 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | — |
| Orbital Period | 35.73 days |
| Orbital Eccentricity (e) | 0.06000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.75 g/cm³ (20.1 km/s vesc) |
| Insolation Flux | — |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 176.000 LY (53.974 pc) |