HAT-P-61 b
Astrophysical Synthesis & Habitability Characterization
HAT-P-61 b is a confirmed gas giant exoplanet orbiting the star HAT-P-61, located approximately 1105.1 light-years (338.84 parsecs) from the Solar System. First announced in 2021 by HATNet using the Transit detection technique (producing an estimated primary transit depth of 0.9701% across the stellar disk), this world measures 10.077 Earth radii (0.9 Jupiter radii) and has a measured mass of 335.945 Earth masses (1.06 Jupiter masses). Combining its mass and radius yields a mean bulk density of 1.81 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 3.31 g⊕ (32.46 m/s²), and an escape velocity of 64.6 km/s.
In its orbital architecture around HAT-P-61, HAT-P-61 b completes one full revolution every 1.902 Earth days at a semi-major axis of 0.0301 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 172.1 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.113 carries the world between 0.0267 AU at periapsis and 0.0335 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1505 K (+1232°C / +2250°F) and receiving 849.50 S⊕ (~1,156,170 W/m²), HAT-P-61 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HAT-P-61 is classified as a stellar host with an effective photospheric temperature of 5,587 K, a radius of 0.938 R☉, a mass of 1.004 M☉, an estimated bolometric luminosity of 0.769 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.6 Gyr and a metallicity of [Fe/H] = 0.194 dex (metal-rich relative to the Sun). From Earth, HAT-P-61 shines at apparent V-band magnitude 13.096 (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-61 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,587 K |
| Stellar Radius | 0.9380 R☉ |
| Stellar Mass | 1.0040 M☉ |
| Bolometric Luminosity | 0.769 L☉ |
| Metallicity [Fe/H] | 0.194 dex |
| Stellar Age | 2.600 Gyr |
| Apparent Magnitude | V: 13.096 · G: 12.939 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.030100 AU |
| Orbital Period | 1.902 days |
| Mean Orbital Velocity | 172.1 km/s |
| Orbital Eccentricity (e) | 0.11300 |
| Orbital Inclination (i) | 83.6200° |
| Mean Bulk Density | 1.81 g/cm³ (64.6 km/s vesc) |
| Insolation Flux | 849.5000 S⊕ (~1,156,170 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1105.100 LY (338.840 pc) |