TOI-5165 b
Astrophysical Synthesis & Habitability Characterization
TOI-5165 b is a confirmed sub-neptune exoplanet orbiting the star TOI-5165, located approximately 800.1 light-years (245.3 parsecs) from the Solar System. First announced in 2026 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.122% across the stellar disk), this world measures 3.32 Earth radii (0.3 Jupiter radii) and has a measured mass of 11 Earth masses. Combining its mass and radius yields a mean bulk density of 1.66 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1 g⊕ (9.81 m/s²), and an escape velocity of 20.4 km/s.
In its orbital architecture around TOI-5165, TOI-5165 b completes one full revolution every 3.577 Earth days. 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 870 K (+597°C / +1107°F) and receiving 95.46 S⊕ (~129,926 W/m²), TOI-5165 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-5165 is classified as an orange K-type star of spectral type K4 with an effective photospheric temperature of 4,642 K, a radius of 0.8716 R☉, a mass of 0.74 M☉, an estimated bolometric luminosity of 0.316 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.066 dex (metal-rich relative to the Sun). From Earth, TOI-5165 shines at apparent V-band magnitude 13.5 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.
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: K2 · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | TOI-5165 |
| Spectral Type | K4 |
| Effective Temp (Teff) | 4,642 K |
| Stellar Radius | 0.8716 R☉ |
| Stellar Mass | 0.7400 M☉ |
| Bolometric Luminosity | 0.316 L☉ |
| Metallicity [Fe/H] | 0.066 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 13.500 · G: 13.182 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | — |
| Orbital Period | 3.577 days |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.66 g/cm³ (20.4 km/s vesc) |
| Insolation Flux | 95.4633 S⊕ (~129,926 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 800.100 LY (245.302 pc) |