HIP 65 A b
Astrophysical Synthesis & Habitability Characterization
HIP 65 A b is a confirmed gas giant exoplanet orbiting the star HIP 65 A, located approximately 201.5 light-years (61.79 parsecs) from the Solar System. First announced in 2020 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 8.2974% across the stellar disk), this world measures 22.754 Earth radii (2.03 Jupiter radii) and has a measured mass of 1021.188 Earth masses (3.21 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.48 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.97 g⊕ (19.32 m/s²), and an escape velocity of 74.9 km/s.
In its orbital architecture around HIP 65 A, HIP 65 A b completes one full revolution every 0.981 Earth days at a semi-major axis of 0.01782 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 197.6 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 1411 K (+1138°C / +2080°F) and receiving 661.00 S⊕ (~899,621 W/m²), HIP 65 A b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HIP 65 A is classified as an orange K-type star of spectral type K4 V with an effective photospheric temperature of 4,590 K, a radius of 0.7242 R☉, a mass of 0.781 M☉, an estimated bolometric luminosity of 0.209 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.1 Gyr and a metallicity of [Fe/H] = 0.18 dex (metal-rich relative to the Sun). From Earth, HIP 65 A shines at apparent V-band magnitude 11 (faint and requiring research-grade or CCD telescopic photometry) in the Southern 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: Transiting Exoplanet Survey Satellite (TESS) · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HIP 65 A |
| Spectral Type | K4 V |
| Effective Temp (Teff) | 4,590 K |
| Stellar Radius | 0.7242 R☉ |
| Stellar Mass | 0.7810 M☉ |
| Bolometric Luminosity | 0.209 L☉ |
| Metallicity [Fe/H] | 0.180 dex |
| Stellar Age | 4.100 Gyr |
| Apparent Magnitude | V: 11.000 · G: 10.590 |
| System Architecture | 2 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.017820 AU |
| Orbital Period | 0.981 days |
| Mean Orbital Velocity | 197.6 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 77.1800° |
| Mean Bulk Density | 0.48 g/cm³ (74.9 km/s vesc) |
| Insolation Flux | 661.0000 S⊕ (~899,621 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 201.500 LY (61.786 pc) |