K2-173 b
Astrophysical Synthesis & Habitability Characterization
K2-173 b is a confirmed super-earth exoplanet orbiting the star K2-173, located approximately 745.7 light-years (228.64 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0306% across the stellar disk), this world measures 1.608 Earth radii and has a measured mass of 3.22 Earth masses. Combining its mass and radius yields a mean bulk density of 4.27 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.25 g⊕ (12.26 m/s²), and an escape velocity of 15.8 km/s.
In its orbital architecture around K2-173, K2-173 b completes one full revolution every 5.869 Earth days.
ℹ️ Thermal & Atmospheric Regime: Current photometric and spectroscopic constraints for K2-173 b place it outside the conservative habitable zone definition pending further atmospheric characterization.
The host star K2-173 is classified as a stellar host with an effective photospheric temperature of 5,580 K, a radius of 0.8432 R☉, a mass of 0.8815 M☉, an estimated bolometric luminosity of 0.618 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.25 dex (metal-poor relative to the Sun). From Earth, K2-173 shines at apparent V-band magnitude 12.523 (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 | K2-173 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,580 K |
| Stellar Radius | 0.8432 R☉ |
| Stellar Mass | 0.8815 M☉ |
| Bolometric Luminosity | 0.618 L☉ |
| Metallicity [Fe/H] | -0.250 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 12.523 · G: 12.185 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | — |
| Orbital Period | 5.869 days |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 87.8256° |
| Mean Bulk Density | 4.27 g/cm³ (15.8 km/s vesc) |
| Insolation Flux | — |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 745.700 LY (228.641 pc) |