ups Leo b
Astrophysical Synthesis & Habitability Characterization
ups Leo b is a confirmed gas giant exoplanet orbiting the star ups Leo, located approximately 171.5 light-years (52.6 parsecs) from the Solar System. First announced in 2021 by Okayama Astrophysical Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 14.2 Earth radii (1.27 Jupiter radii) and has a measured mass of 162.092 Earth masses (0.51 Jupiter masses). Combining its mass and radius yields a mean bulk density of 0.31 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.8 g⊕ (7.85 m/s²), and an escape velocity of 37.8 km/s.
In its orbital architecture around ups Leo, ups Leo b completes one full revolution every 385.2 Earth days (1.05Julian years) at a semi-major axis of 1.18 AU (comparable to the inner terrestrial zone between Venus, Earth at 1.00 AU, and Mars at 1.52 AU). Its mean orbital velocity is approximately 33.3 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.32, swinging from 0.8024 AU at periapsis out to 1.5576 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 719 K (+446°C / +835°F) and receiving 45.32 S⊕ (~61,677 W/m²), ups Leo b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star ups Leo is classified as a solar-type yellow star of spectral type G9 III with an effective photospheric temperature of 4,836 K, a radius of 11.22 R☉, a mass of 1.48 M☉, an estimated bolometric luminosity of 61.776 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.2 dex (metal-poor relative to the Sun). From Earth, ups Leo shines at apparent V-band magnitude 4.305 (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: Okayama Astrophysical Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | ups Leo |
| Spectral Type | G9 III |
| Effective Temp (Teff) | 4,836 K |
| Stellar Radius | 11.2200 R☉ |
| Stellar Mass | 1.4800 M☉ |
| Bolometric Luminosity | 61.776 L☉ |
| Metallicity [Fe/H] | -0.200 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 4.305 · G: 4.030 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 1.180000 AU |
| Orbital Period | 385.2 days |
| Mean Orbital Velocity | 33.3 km/s |
| Orbital Eccentricity (e) | 0.32000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 0.31 g/cm³ (37.8 km/s vesc) |
| Insolation Flux | 45.3174 S⊕ (~61,677 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 171.500 LY (52.597 pc) |