HU Aqr AB c
Astrophysical Synthesis & Habitability Characterization
HU Aqr AB c is a confirmed gas giant exoplanet orbiting the star HU Aqr, located approximately 626.9 light-years (192.2 parsecs) from the Solar System. First announced in 2011 by Yunnan Astronomical Observatory using the Eclipse Timing Variations detection technique, this world measures 12.9 Earth radii (1.15 Jupiter radii) and has a measured mass of 1430.235 Earth masses (4.5 Jupiter masses). Combining its mass and radius yields a mean bulk density of 3.67 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 8.59 g⊕ (84.24 m/s²), and an escape velocity of 117.8 km/s.
In its orbital architecture around HU Aqr, HU Aqr AB c completes one full revolution every 4368 Earth days (11.96Julian years) at a semi-major axis of 5.4 AU (a wide outer-system orbit beyond Jupiter's 5.20 AU distance in our Solar System). Its mean orbital velocity is approximately 13.4 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.51, swinging from 2.646 AU at periapsis out to 8.154 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 12.900 R⊕, HU Aqr AB c exceeds the empirical ~1.8–2.2 R⊕ Fulton radius valley threshold, indicating a substantial hydrogen-helium or supercritical volatile envelope without a conventional solid terrestrial surface.
The host star HU Aqr is classified as a stellar host with an effective photospheric temperature of 5,952 K, a mass of 0.88 M☉. From Earth, HU Aqr shines at apparent V-band magnitude 16.183 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The HU Aqr system is a multi-planet architecture hosting 2 confirmed worlds, with HU Aqr AB c sharing its stellar neighborhood alongside HU Aqr AB 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: Yunnan Astronomical Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HU Aqr |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,952 K |
| Stellar Radius | — |
| Stellar Mass | 0.8800 M☉ |
| Metallicity [Fe/H] | — |
| Stellar Age | — |
| Apparent Magnitude | V: 16.183 · G: 16.472 |
| System Architecture | 2 Stars, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 5.400000 AU |
| Orbital Period | 4368 days |
| Mean Orbital Velocity | 13.4 km/s |
| Orbital Eccentricity (e) | 0.51000 |
| Orbital Inclination (i) | 90.0000° |
| Mean Bulk Density | 3.67 g/cm³ (117.8 km/s vesc) |
| Insolation Flux | — |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 626.900 LY (192.198 pc) |