HIP 54373 c
Astrophysical Synthesis & Habitability Characterization
HIP 54373 c is a confirmed sub-neptune exoplanet orbiting the star HIP 54373, located approximately 61 light-years (18.72 parsecs) from the Solar System. First announced in 2019 by Las Campanas Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 3.57 Earth radii (0.32 Jupiter radii) and has a measured mass of 12.44 Earth masses. Combining its mass and radius yields a mean bulk density of 1.51 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.98 g⊕ (9.61 m/s²), and an escape velocity of 20.9 km/s.
In its orbital architecture around HIP 54373, HIP 54373 c completes one full revolution every 15.144 Earth days at a semi-major axis of 0.099 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 71.1 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.2 carries the world between 0.0792 AU at periapsis and 0.1188 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 463 K (+190°C / +374°F) and receiving 6.11 S⊕ (~8,321 W/m²), HIP 54373 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star HIP 54373 is classified as an orange K-type star of spectral type K5 V with an effective photospheric temperature of 4,021 K, a radius of 0.565 R☉, a mass of 0.57 M☉, an estimated bolometric luminosity of 0.075 L☉. From Earth, HIP 54373 shines at apparent V-band magnitude 10.38 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The HIP 54373 system is a multi-planet architecture hosting 2 confirmed worlds, with HIP 54373 c sharing its stellar neighborhood alongside HIP 54373 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: Las Campanas Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HIP 54373 |
| Spectral Type | K5 V |
| Effective Temp (Teff) | 4,021 K |
| Stellar Radius | 0.5650 R☉ |
| Stellar Mass | 0.5700 M☉ |
| Bolometric Luminosity | 0.075 L☉ |
| Metallicity [Fe/H] | — |
| Stellar Age | — |
| Apparent Magnitude | V: 10.380 · G: 9.641 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.099000 AU |
| Orbital Period | 15.144 days |
| Mean Orbital Velocity | 71.1 km/s |
| Orbital Eccentricity (e) | 0.20000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.51 g/cm³ (20.9 km/s vesc) |
| Insolation Flux | 6.1142 S⊕ (~8,321 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 61.000 LY (18.717 pc) |