HATS-59 c
Astrophysical Synthesis & Habitability Characterization
HATS-59 c is a confirmed gas giant exoplanet orbiting the star HATS-59, located approximately 2096.8 light-years (642.88 parsecs) from the Solar System. First announced in 2018 by HATSouth using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 12.3 Earth radii (1.1 Jupiter radii) and has a measured mass of 4036.441 Earth masses (12.7 Jupiter masses). Combining its mass and radius yields a mean bulk density of 11.96 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 26.68 g⊕ (261.64 m/s²), and an escape velocity of 202.6 km/s.
In its orbital architecture around HATS-59, HATS-59 c completes one full revolution every 1422 Earth days (3.89Julian years) at a semi-major axis of 2.504 AU (corresponding to the middle-system regime between Mars at 1.52 AU and Jupiter at 5.20 AU). Its mean orbital velocity is approximately 19.2 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.083 carries the world between 2.2962 AU at periapsis and 2.7118 AU at apoapsis, driving measurable seasonal insolation cycles.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 176 K (-97°C / -143°F) and an incident flux of 0.16 S⊕ (~216 W/m²), surface water and volatile species on HATS-59 c would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star HATS-59 is classified as a stellar host with an effective photospheric temperature of 5,670 K, a radius of 1.036 R☉, a mass of 1.038 M☉, an estimated bolometric luminosity of 0.995 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.3 Gyr and a metallicity of [Fe/H] = 0.18 dex (metal-rich relative to the Sun). From Earth, HATS-59 shines at apparent V-band magnitude 14.033 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The HATS-59 system is a multi-planet architecture hosting 2 confirmed worlds, with HATS-59 c sharing its stellar neighborhood alongside HATS-59 b.
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: HATSouth · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HATS-59 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,670 K |
| Stellar Radius | 1.0360 R☉ |
| Stellar Mass | 1.0380 M☉ |
| Bolometric Luminosity | 0.995 L☉ |
| Metallicity [Fe/H] | 0.180 dex |
| Stellar Age | 4.300 Gyr |
| Apparent Magnitude | V: 14.033 · G: 13.785 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 2.504000 AU |
| Orbital Period | 1422 days |
| Mean Orbital Velocity | 19.2 km/s |
| Orbital Eccentricity (e) | 0.08300 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 11.96 g/cm³ (202.6 km/s vesc) |
| Insolation Flux | 0.1590 S⊕ (~216 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2096.800 LY (642.884 pc) |