HIP 71135 b
Astrophysical Synthesis & Habitability Characterization
HIP 71135 b is a confirmed sub-neptune exoplanet orbiting the star HIP 71135, located approximately 105.4 light-years (32.33 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 4.55 Earth radii (0.41 Jupiter radii) and has a measured mass of 18.8 Earth masses. Combining its mass and radius yields a mean bulk density of 1.1 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.91 g⊕ (8.92 m/s²), and an escape velocity of 22.7 km/s.
In its orbital architecture around HIP 71135, HIP 71135 b completes one full revolution every 87.19 Earth days at a semi-major axis of 0.335 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 41.8 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.21 carries the world between 0.2647 AU at periapsis and 0.4054 AU at apoapsis, driving measurable seasonal insolation cycles.
☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 4.550 R⊕, HIP 71135 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 71135 is classified as a low-mass red dwarf of spectral type M1 with an effective photospheric temperature of 4,146 K, a radius of 0.6813 R☉, a mass of 0.66 M☉, an estimated bolometric luminosity of 0.123 L☉. From Earth, HIP 71135 shines at apparent V-band magnitude 10.53 (faint and requiring research-grade or CCD telescopic photometry) 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: Las Campanas Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HIP 71135 |
| Spectral Type | M1 |
| Effective Temp (Teff) | 4,146 K |
| Stellar Radius | 0.6813 R☉ |
| Stellar Mass | 0.6600 M☉ |
| Bolometric Luminosity | 0.123 L☉ |
| Metallicity [Fe/H] | — |
| Stellar Age | — |
| Apparent Magnitude | V: 10.530 · G: 9.958 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.335000 AU |
| Orbital Period | 87.19 days |
| Mean Orbital Velocity | 41.8 km/s |
| Orbital Eccentricity (e) | 0.21000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.1 g/cm³ (22.7 km/s vesc) |
| Insolation Flux | 1.1013 S⊕ (~1,499 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 105.400 LY (32.331 pc) |