TOI-1117 c
Astrophysical Synthesis & Habitability Characterization
TOI-1117 c is a confirmed sub-neptune exoplanet orbiting the star TOI-1117, located approximately 546.6 light-years (167.6 parsecs) from the Solar System. First announced in 2025 by La Silla Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 2.91 Earth radii and has a measured mass of 8.78 Earth masses. Combining its mass and radius yields a mean bulk density of 1.96 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.04 g⊕ (10.2 m/s²), and an escape velocity of 19.4 km/s.
In its orbital architecture around TOI-1117, TOI-1117 c completes one full revolution every 4.579 Earth days at a semi-major axis of 0.0534 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 126.9 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 1210 K (+937°C / +1719°F) and receiving 355.00 S⊕ (~483,155 W/m²), TOI-1117 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-1117 is classified as a solar-type yellow star of spectral type G5 V with an effective photospheric temperature of 5,635 K, a radius of 1.05 R☉, a mass of 0.97 M☉, an estimated bolometric luminosity of 0.997 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.42 Gyr and a metallicity of [Fe/H] = 0.136 dex (metal-rich relative to the Sun). From Earth, TOI-1117 shines at apparent V-band magnitude 11.016 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The TOI-1117 system is a multi-planet architecture hosting 3 confirmed worlds, with TOI-1117 c sharing its stellar neighborhood alongside TOI-1117 b, TOI-1117 d.
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: La Silla Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | TOI-1117 |
| Spectral Type | G5 V |
| Effective Temp (Teff) | 5,635 K |
| Stellar Radius | 1.0500 R☉ |
| Stellar Mass | 0.9700 M☉ |
| Bolometric Luminosity | 0.997 L☉ |
| Metallicity [Fe/H] | 0.136 dex |
| Stellar Age | 4.420 Gyr |
| Apparent Magnitude | V: 11.016 · G: 10.862 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.053400 AU |
| Orbital Period | 4.579 days |
| Mean Orbital Velocity | 126.9 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.96 g/cm³ (19.4 km/s vesc) |
| Insolation Flux | 355.0000 S⊕ (~483,155 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 546.600 LY (167.598 pc) |