91 Aqr b
Astrophysical Synthesis & Habitability Characterization
91 Aqr b is a confirmed gas giant exoplanet orbiting the star 91 Aqr, located approximately 143.6 light-years (44.03 parsecs) from the Solar System. First announced in 2013 by Lick Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13.1 Earth radii (1.17 Jupiter radii) and has a measured mass of 1017 Earth masses (3.2 Jupiter masses). Combining its mass and radius yields a mean bulk density of 2.49 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 5.93 g⊕ (58.15 m/s²), and an escape velocity of 98.6 km/s.
In its orbital architecture around 91 Aqr, 91 Aqr b completes one full revolution every 181.4 Earth days at a semi-major axis of 0.7 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 42 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.027 (ranging from 0.6811 AU at periapsis to 0.7189 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 892 K (+619°C / +1146°F) and receiving 100.51 S⊕ (~136,789 W/m²), 91 Aqr b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star 91 Aqr is classified as an orange K-type star of spectral type K0 III with an effective photospheric temperature of 4,665 K, a radius of 11 R☉, a mass of 1.4 M☉, an estimated bolometric luminosity of 51.414 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.56 Gyr and a metallicity of [Fe/H] = -0.03 dex (near-solar heavy-element abundance). From Earth, 91 Aqr shines at apparent V-band magnitude 4.239 (visible to the unaided human eye under dark skies) 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: Lick Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | 91 Aqr |
| Spectral Type | K0 III |
| Effective Temp (Teff) | 4,665 K |
| Stellar Radius | 11.0000 R☉ |
| Stellar Mass | 1.4000 M☉ |
| Bolometric Luminosity | 51.414 L☉ |
| Metallicity [Fe/H] | -0.030 dex |
| Stellar Age | 3.560 Gyr |
| Apparent Magnitude | V: 4.239 · G: 3.953 |
| System Architecture | 3 Stars, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.700000 AU |
| Orbital Period | 181.4 days |
| Mean Orbital Velocity | 42 km/s |
| Orbital Eccentricity (e) | 0.02700 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 2.49 g/cm³ (98.6 km/s vesc) |
| Insolation Flux | 100.5060 S⊕ (~136,789 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 143.600 LY (44.030 pc) |