HIP 38594 b
Astrophysical Synthesis & Habitability Characterization
HIP 38594 b is a confirmed sub-neptune exoplanet orbiting the star HIP 38594, located approximately 58 light-years (17.79 parsecs) from the Solar System. First announced in 2020 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 2.77 Earth radii and has a measured mass of 8.1 Earth masses. Combining its mass and radius yields a mean bulk density of 2.1 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.06 g⊕ (10.4 m/s²), and an escape velocity of 19.1 km/s.
In its orbital architecture around HIP 38594, HIP 38594 b completes one full revolution every 60.722 Earth days at a semi-major axis of 0.256 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 45.9 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.17 carries the world between 0.2125 AU at periapsis and 0.2995 AU at apoapsis, driving measurable seasonal insolation cycles.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 2.770 R⊕, HIP 38594 b 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 HIP 38594 is classified as a low-mass red dwarf of spectral type M0 with an effective photospheric temperature of 4,086 K, a radius of 0.6266 R☉, a mass of 0.61 M☉, an estimated bolometric luminosity of 0.098 L☉. From Earth, HIP 38594 shines at apparent V-band magnitude 9.75 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere. The HIP 38594 system is a multi-planet architecture hosting 2 confirmed worlds, with HIP 38594 b sharing its stellar neighborhood alongside HIP 38594 c.
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: Multiple Observatories · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HIP 38594 |
| Spectral Type | M0 |
| Effective Temp (Teff) | 4,086 K |
| Stellar Radius | 0.6266 R☉ |
| Stellar Mass | 0.6100 M☉ |
| Bolometric Luminosity | 0.098 L☉ |
| Metallicity [Fe/H] | — |
| Stellar Age | — |
| Apparent Magnitude | V: 9.750 · G: 9.085 |
| System Architecture | 2 Stars, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.256000 AU |
| Orbital Period | 60.722 days |
| Mean Orbital Velocity | 45.9 km/s |
| Orbital Eccentricity (e) | 0.17000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 2.1 g/cm³ (19.1 km/s vesc) |
| Insolation Flux | 1.3216 S⊕ (~1,799 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 58.000 LY (17.789 pc) |