K2-277 b
Astrophysical Synthesis & Habitability Characterization
K2-277 b is a confirmed sub-neptune exoplanet orbiting the star K2-277, located approximately 369 light-years (113.12 parsecs) from the Solar System. First announced in 2018 by K2 using the Transit detection technique (producing an estimated primary transit depth of 0.0424% across the stellar disk), this world measures 2.186 Earth radii and has a measured mass of 7.4 Earth masses. Combining its mass and radius yields a mean bulk density of 3.91 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.55 g⊕ (15.2 m/s²), and an escape velocity of 20.6 km/s.
In its orbital architecture around K2-277, K2-277 b completes one full revolution every 6.327 Earth days at a semi-major axis of 0.0664 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 114.2 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.52, swinging from 0.0319 AU at periapsis out to 0.1009 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1049 K (+776°C / +1429°F) and receiving 195.00 S⊕ (~265,395 W/m²), K2-277 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-277 is classified as a stellar host with an effective photospheric temperature of 5,680 K, a radius of 0.973 R☉, a mass of 0.974 M☉, an estimated bolometric luminosity of 0.884 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.9 Gyr and a metallicity of [Fe/H] = 0.078 dex (metal-rich relative to the Sun). From Earth, K2-277 shines at apparent V-band magnitude 10.364 (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 | K2-277 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,680 K |
| Stellar Radius | 0.9730 R☉ |
| Stellar Mass | 0.9740 M☉ |
| Bolometric Luminosity | 0.884 L☉ |
| Metallicity [Fe/H] | 0.078 dex |
| Stellar Age | 4.900 Gyr |
| Apparent Magnitude | V: 10.364 · G: 10.121 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.066400 AU |
| Orbital Period | 6.327 days |
| Mean Orbital Velocity | 114.2 km/s |
| Orbital Eccentricity (e) | 0.52000 |
| Orbital Inclination (i) | 86.8300° |
| Mean Bulk Density | 3.91 g/cm³ (20.6 km/s vesc) |
| Insolation Flux | 195.0000 S⊕ (~265,395 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 369.000 LY (113.123 pc) |