K2-29 b
Astrophysical Synthesis & Habitability Characterization
K2-29 b is a confirmed gas giant exoplanet orbiting the star K2-29, located approximately 582.1 light-years (178.48 parsecs) from the Solar System. First announced in 2016 by K2 using the Transit detection technique (producing an estimated primary transit depth of 2.022% across the stellar disk), this world measures 13.339 Earth radii (1.19 Jupiter radii) and has a measured mass of 232.016 Earth masses (0.73 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.54 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.3 g⊕ (12.75 m/s²), and an escape velocity of 46.7 km/s.
In its orbital architecture around K2-29, K2-29 b completes one full revolution every 3.259 Earth days at a semi-major axis of 0.04217 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 140.8 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.066 carries the world between 0.0394 AU at periapsis and 0.045 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1171 K (+898°C / +1648°F) and receiving 293.00 S⊕ (~398,773 W/m²), K2-29 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star K2-29 is classified as a solar-type yellow star of spectral type G7 V with an effective photospheric temperature of 5,358 K, a radius of 0.86 R☉, a mass of 0.94 M☉, an estimated bolometric luminosity of 0.547 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.6 Gyr and a metallicity of [Fe/H] = 0.16 dex (metal-rich relative to the Sun). From Earth, K2-29 shines at apparent V-band magnitude 12.532 (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 | K2-29 |
| Spectral Type | G7 V |
| Effective Temp (Teff) | 5,358 K |
| Stellar Radius | 0.8600 R☉ |
| Stellar Mass | 0.9400 M☉ |
| Bolometric Luminosity | 0.547 L☉ |
| Metallicity [Fe/H] | 0.160 dex |
| Stellar Age | 2.600 Gyr |
| Apparent Magnitude | V: 12.532 · G: 12.201 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.042170 AU |
| Orbital Period | 3.259 days |
| Mean Orbital Velocity | 140.8 km/s |
| Orbital Eccentricity (e) | 0.06600 |
| Orbital Inclination (i) | 86.6560° |
| Mean Bulk Density | 0.54 g/cm³ (46.7 km/s vesc) |
| Insolation Flux | 293.0000 S⊕ (~398,773 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 582.100 LY (178.475 pc) |