TOI-776 c
Astrophysical Synthesis & Habitability Characterization
TOI-776 c is a confirmed sub-neptune exoplanet orbiting the star TOI-776, located approximately 88.6 light-years (27.17 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 0.1177% across the stellar disk), this world measures 2.047 Earth radii and has a measured mass of 6.9 Earth masses. Combining its mass and radius yields a mean bulk density of 4.44 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.65 g⊕ (16.18 m/s²), and an escape velocity of 20.5 km/s.
In its orbital architecture around TOI-776, TOI-776 c completes one full revolution every 15.665 Earth days at a semi-major axis of 0.1001 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 69.5 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.089 carries the world between 0.0912 AU at periapsis and 0.109 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 420 K (+147°C / +297°F) and receiving 4.90 S⊕ (~6,669 W/m²), TOI-776 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-776 is classified as a low-mass red dwarf of spectral type M1 V with an effective photospheric temperature of 3,725 K, a radius of 0.547 R☉, a mass of 0.542 M☉, an estimated bolometric luminosity of 0.052 L☉. Stellar evolution modeling indicates an estimated stellar age of 6.1 Gyr and a metallicity of [Fe/H] = -0.21 dex (metal-poor relative to the Sun). From Earth, TOI-776 shines at apparent V-band magnitude 11.536 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The TOI-776 system is a multi-planet architecture hosting 2 confirmed worlds, with TOI-776 c sharing its stellar neighborhood alongside TOI-776 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 | TOI-776 |
| Spectral Type | M1 V |
| Effective Temp (Teff) | 3,725 K |
| Stellar Radius | 0.5470 R☉ |
| Stellar Mass | 0.5420 M☉ |
| Bolometric Luminosity | 0.052 L☉ |
| Metallicity [Fe/H] | -0.210 dex |
| Stellar Age | 6.100 Gyr |
| Apparent Magnitude | V: 11.536 · G: 10.741 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.100100 AU |
| Orbital Period | 15.665 days |
| Mean Orbital Velocity | 69.5 km/s |
| Orbital Eccentricity (e) | 0.08900 |
| Orbital Inclination (i) | 89.4900° |
| Mean Bulk Density | 4.44 g/cm³ (20.5 km/s vesc) |
| Insolation Flux | 4.9000 S⊕ (~6,669 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 88.600 LY (27.170 pc) |