K2-161 b
Astrophysical Synthesis & Habitability Characterization
K2-161 b is a confirmed gas giant exoplanet orbiting the star K2-161, located approximately 2988.6 light-years (916.32 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0477% across the stellar disk), this world measures 6.117 Earth radii (0.55 Jupiter radii) and has a measured mass of 31.1 Earth masses (0.1 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.75 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.83 g⊕ (8.14 m/s²), and an escape velocity of 25.2 km/s.
In its orbital architecture around K2-161, K2-161 b completes one full revolution every 9.283 Earth days.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 6.117 R⊕, K2-161 b exceeds the empirical ~1.8–2.2 R⊕ Fulton radius valley threshold, indicating a substantial hydrogen-helium or supercritical volatile envelope without a conventional solid terrestrial surface.
The host star K2-161 is classified as a stellar host with an effective photospheric temperature of 4,972 K, a radius of 2.5682 R☉, a mass of 0.9869 M☉, an estimated bolometric luminosity of 3.616 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.03 dex (near-solar heavy-element abundance). From Earth, K2-161 shines at apparent V-band magnitude 12.718 (faint and requiring research-grade or CCD telescopic photometry) in the Southern 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 | K2-161 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 4,972 K |
| Stellar Radius | 2.5682 R☉ |
| Stellar Mass | 0.9869 M☉ |
| Bolometric Luminosity | 3.616 L☉ |
| Metallicity [Fe/H] | -0.030 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 12.718 · G: 12.357 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | — |
| Orbital Period | 9.283 days |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 87.2509° |
| Mean Bulk Density | 0.75 g/cm³ (25.2 km/s vesc) |
| Insolation Flux | — |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2988.600 LY (916.319 pc) |