HAT-P-68 b
Astrophysical Synthesis & Habitability Characterization
HAT-P-68 b is a confirmed gas giant exoplanet orbiting the star HAT-P-68, located approximately 659.3 light-years (202.15 parsecs) from the Solar System. First announced in 2020 by HATNet using the Transit detection technique (producing an estimated primary transit depth of 2.7026% across the stellar disk), this world measures 12.016 Earth radii (1.07 Jupiter radii) and has a measured mass of 230.109 Earth masses (0.72 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.73 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.59 g⊕ (15.59 m/s²), and an escape velocity of 49 km/s.
In its orbital architecture around HAT-P-68, HAT-P-68 b completes one full revolution every 2.298 Earth days at a semi-major axis of 0.02996 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 141.8 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.041 (ranging from 0.0287 AU at periapsis to 0.0312 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1028 K (+755°C / +1391°F) and receiving 184.80 S⊕ (~251,513 W/m²), HAT-P-68 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HAT-P-68 is classified as an orange K-type star of spectral type K with an effective photospheric temperature of 4,508 K, a radius of 0.6701 R☉, a mass of 0.6785 M☉, an estimated bolometric luminosity of 0.166 L☉. Stellar evolution modeling indicates an estimated stellar age of 11.1 Gyr and a metallicity of [Fe/H] = -0.059 dex (near-solar heavy-element abundance). From Earth, HAT-P-68 shines at apparent V-band magnitude 13.802 (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-68 |
| Spectral Type | K |
| Effective Temp (Teff) | 4,508 K |
| Stellar Radius | 0.6701 R☉ |
| Stellar Mass | 0.6785 M☉ |
| Bolometric Luminosity | 0.166 L☉ |
| Metallicity [Fe/H] | -0.059 dex |
| Stellar Age | 11.100 Gyr |
| Apparent Magnitude | V: 13.802 · G: 13.544 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.029960 AU |
| Orbital Period | 2.298 days |
| Mean Orbital Velocity | 141.8 km/s |
| Orbital Eccentricity (e) | 0.04100 |
| Orbital Inclination (i) | 88.7300° |
| Mean Bulk Density | 0.73 g/cm³ (49 km/s vesc) |
| Insolation Flux | 184.8000 S⊕ (~251,513 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 659.300 LY (202.152 pc) |