HAT-P-26 b
Astrophysical Synthesis & Habitability Characterization
HAT-P-26 b is a confirmed gas giant exoplanet orbiting the star HAT-P-26, located approximately 462.6 light-years (141.84 parsecs) from the Solar System. First announced in 2010 by HATNet using the Transit detection technique (producing an estimated primary transit depth of 0.5538% across the stellar disk), this world measures 7.062 Earth radii (0.63 Jupiter radii) and has a measured mass of 22.248 Earth masses. Combining its mass and radius yields a mean bulk density of 0.35 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.45 g⊕ (4.41 m/s²), and an escape velocity of 19.9 km/s.
In its orbital architecture around HAT-P-26, HAT-P-26 b completes one full revolution every 4.235 Earth days at a semi-major axis of 0.04748 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 122 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.12 carries the world between 0.0418 AU at periapsis and 0.0532 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1080 K (+807°C / +1485°F) and receiving 185.07 S⊕ (~251,886 W/m²), HAT-P-26 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HAT-P-26 is classified as an orange K-type star of spectral type K1 with an effective photospheric temperature of 5,079 K, a radius of 0.87 R☉, a mass of 1.12 M☉, an estimated bolometric luminosity of 0.452 L☉. Stellar evolution modeling indicates an estimated stellar age of 9 Gyr and a metallicity of [Fe/H] = -0.04 dex (near-solar heavy-element abundance). From Earth, HAT-P-26 shines at apparent V-band magnitude 11.757 (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: HATNet · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HAT-P-26 |
| Spectral Type | K1 |
| Effective Temp (Teff) | 5,079 K |
| Stellar Radius | 0.8700 R☉ |
| Stellar Mass | 1.1200 M☉ |
| Bolometric Luminosity | 0.452 L☉ |
| Metallicity [Fe/H] | -0.040 dex |
| Stellar Age | 9.000 Gyr |
| Apparent Magnitude | V: 11.757 · G: 11.464 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.047480 AU |
| Orbital Period | 4.235 days |
| Mean Orbital Velocity | 122 km/s |
| Orbital Eccentricity (e) | 0.12000 |
| Orbital Inclination (i) | 88.6000° |
| Mean Bulk Density | 0.35 g/cm³ (19.9 km/s vesc) |
| Insolation Flux | 185.0743 S⊕ (~251,886 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 462.600 LY (141.837 pc) |