K2-127 b
Astrophysical Synthesis & Habitability Characterization
K2-127 b is a confirmed gas giant exoplanet orbiting the star K2-127, located approximately 2315.7 light-years (710 parsecs) from the Solar System. First announced in 2017 by K2 using the Transit detection technique (producing an estimated primary transit depth of 1.3518% across the stellar disk), this world measures 8.37 Earth radii (0.75 Jupiter radii) and has a measured mass of 52.9 Earth masses (0.17 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.5 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.76 g⊕ (7.45 m/s²), and an escape velocity of 28.1 km/s.
In its orbital architecture around K2-127, K2-127 b completes one full revolution every 3.588 Earth days at a semi-major axis of 0.0411 AU (an ultra-close orbit less than one-seventh of Mercury's 0.387 AU distance from the Sun, where strong stellar tidal forces typically induce synchronous rotation). Its mean orbital velocity is approximately 124.6 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.12 carries the world between 0.0362 AU at periapsis and 0.046 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 809 K (+536°C / +997°F) and receiving 105.60 S⊕ (~143,722 W/m²), K2-127 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-127 is classified as a stellar host with an effective photospheric temperature of 4,575 K, a radius of 0.66 R☉, a mass of 0.72 M☉, an estimated bolometric luminosity of 0.171 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.11 dex (metal-poor relative to the Sun). From Earth, K2-127 shines at apparent V-band magnitude 15.041 (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 | K2-127 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 4,575 K |
| Stellar Radius | 0.6600 R☉ |
| Stellar Mass | 0.7200 M☉ |
| Bolometric Luminosity | 0.171 L☉ |
| Metallicity [Fe/H] | -0.110 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 15.041 · G: 14.787 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.041100 AU |
| Orbital Period | 3.588 days |
| Mean Orbital Velocity | 124.6 km/s |
| Orbital Eccentricity (e) | 0.12000 |
| Orbital Inclination (i) | 87.2200° |
| Mean Bulk Density | 0.5 g/cm³ (28.1 km/s vesc) |
| Insolation Flux | 105.6000 S⊕ (~143,722 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2315.700 LY (709.999 pc) |