K2-80 d
Astrophysical Synthesis & Habitability Characterization
K2-80 d is a confirmed sub-neptune exoplanet orbiting the star K2-80, located approximately 654.9 light-years (200.8 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0773% across the stellar disk), this world measures 2.552 Earth radii and has a measured mass of 7.04 Earth masses. Combining its mass and radius yields a mean bulk density of 2.34 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.08 g⊕ (10.59 m/s²), and an escape velocity of 18.6 km/s.
In its orbital architecture around K2-80, K2-80 d completes one full revolution every 28.867 Earth days.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 2.552 R⊕, K2-80 d 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 K2-80 is classified as a stellar host with an effective photospheric temperature of 5,377 K, a radius of 0.8415 R☉, a mass of 0.9131 M☉, an estimated bolometric luminosity of 0.531 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.07 dex (metal-rich relative to the Sun). From Earth, K2-80 shines at apparent V-band magnitude 12.694 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The K2-80 system is a multi-planet architecture hosting 3 confirmed worlds, with K2-80 d sharing its stellar neighborhood alongside K2-80 c, K2-80 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: K2 · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | K2-80 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,377 K |
| Stellar Radius | 0.8415 R☉ |
| Stellar Mass | 0.9131 M☉ |
| Bolometric Luminosity | 0.531 L☉ |
| Metallicity [Fe/H] | 0.070 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 12.694 · G: 12.377 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | — |
| Orbital Period | 28.867 days |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 89.3968° |
| Mean Bulk Density | 2.34 g/cm³ (18.6 km/s vesc) |
| Insolation Flux | — |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 654.900 LY (200.802 pc) |