KELT-2 A b
Astrophysical Synthesis & Habitability Characterization
KELT-2 A b is a confirmed gas giant exoplanet orbiting the star KELT-2 A, located approximately 437.2 light-years (134.06 parsecs) from the Solar System. First announced in 2012 by KELT using the Transit detection technique (producing an estimated primary transit depth of 0.5167% across the stellar disk), this world measures 15.132 Earth radii (1.35 Jupiter radii) and has a measured mass of 540.311 Earth masses (1.7 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.86 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 2.36 g⊕ (23.14 m/s²), and an escape velocity of 66.8 km/s.
In its orbital architecture around KELT-2 A, KELT-2 A b completes one full revolution every 4.114 Earth days at a semi-major axis of 0.05497 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 145.4 km/s (compared to Earth's 29.8 km/s). The orbit is modeled as circular (e = 0.00), maintaining a constant stellar distance throughout its year.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 2080 K (+1807°C / +3285°F) and receiving 3,108.45 S⊕ (~4,230,600 W/m²), KELT-2 A b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star KELT-2 A is classified as a warm F-type star of spectral type F8 with an effective photospheric temperature of 6,327 K, a radius of 1.93 R☉, a mass of 1.54 M☉, an estimated bolometric luminosity of 5.355 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.97 Gyr and a metallicity of [Fe/H] = 0 dex (near-solar heavy-element abundance). From Earth, KELT-2 A shines at apparent V-band magnitude 8.68 (accessible to binoculars and small amateur telescopes) 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: KELT · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | KELT-2 A |
| Spectral Type | F8 |
| Effective Temp (Teff) | 6,327 K |
| Stellar Radius | 1.9300 R☉ |
| Stellar Mass | 1.5400 M☉ |
| Bolometric Luminosity | 5.355 L☉ |
| Metallicity [Fe/H] | 0.000 dex |
| Stellar Age | 3.970 Gyr |
| Apparent Magnitude | V: 8.680 · G: 8.584 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.054970 AU |
| Orbital Period | 4.114 days |
| Mean Orbital Velocity | 145.4 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 88.6000° |
| Mean Bulk Density | 0.86 g/cm³ (66.8 km/s vesc) |
| Insolation Flux | 3108.4500 S⊕ (~4,230,600 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 437.200 LY (134.058 pc) |