HAT-P-23 b
Astrophysical Synthesis & Habitability Characterization
HAT-P-23 b is a confirmed gas giant exoplanet orbiting the star HAT-P-23, located approximately 1189.9 light-years (364.81 parsecs) from the Solar System. First announced in 2010 by HATNet using the Transit detection technique (producing an estimated primary transit depth of 1.3656% across the stellar disk), this world measures 15.334 Earth radii (1.37 Jupiter radii) and has a measured mass of 664.237 Earth masses (2.09 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.02 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 2.82 g⊕ (27.65 m/s²), and an escape velocity of 73.6 km/s.
In its orbital architecture around HAT-P-23, HAT-P-23 b completes one full revolution every 1.213 Earth days at a semi-major axis of 0.0232 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 208.1 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.106 carries the world between 0.0207 AU at periapsis and 0.0257 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 2056 K (+1783°C / +3241°F) and receiving 2,796.23 S⊕ (~3,805,675 W/m²), HAT-P-23 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HAT-P-23 is classified as a solar-type yellow star of spectral type G0 with an effective photospheric temperature of 5,905 K, a radius of 1.203 R☉, a mass of 1.13 M☉, an estimated bolometric luminosity of 1.579 L☉. Stellar evolution modeling indicates an estimated stellar age of 4 Gyr and a metallicity of [Fe/H] = 0.15 dex (metal-rich relative to the Sun). From Earth, HAT-P-23 shines at apparent V-band magnitude 11.937 (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-23 |
| Spectral Type | G0 |
| Effective Temp (Teff) | 5,905 K |
| Stellar Radius | 1.2030 R☉ |
| Stellar Mass | 1.1300 M☉ |
| Bolometric Luminosity | 1.579 L☉ |
| Metallicity [Fe/H] | 0.150 dex |
| Stellar Age | 4.000 Gyr |
| Apparent Magnitude | V: 11.937 · G: 12.174 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.023200 AU |
| Orbital Period | 1.213 days |
| Mean Orbital Velocity | 208.1 km/s |
| Orbital Eccentricity (e) | 0.10600 |
| Orbital Inclination (i) | 85.1000° |
| Mean Bulk Density | 1.02 g/cm³ (73.6 km/s vesc) |
| Insolation Flux | 2796.2342 S⊕ (~3,805,675 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1189.900 LY (364.813 pc) |