LSPM J2116+0234 b
Astrophysical Synthesis & Habitability Characterization
LSPM J2116+0234 b is a confirmed sub-neptune exoplanet orbiting the star LSPM J2116+0234, located approximately 57.5 light-years (17.63 parsecs) from the Solar System. First announced in 2019 by Calar Alto Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 3.71 Earth radii (0.33 Jupiter radii) and has a measured mass of 13.3 Earth masses. Combining its mass and radius yields a mean bulk density of 1.44 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.97 g⊕ (9.51 m/s²), and an escape velocity of 21.2 km/s.
In its orbital architecture around LSPM J2116+0234, LSPM J2116+0234 b completes one full revolution every 14.44 Earth days at a semi-major axis of 0.0876 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 66 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.183 carries the world between 0.0716 AU at periapsis and 0.1036 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 372 K (+99°C / +210°F) and receiving 2.61 S⊕ (~3,547 W/m²), LSPM J2116+0234 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star LSPM J2116+0234 is classified as a low-mass red dwarf of spectral type M3.0 V with an effective photospheric temperature of 3,475 K, a radius of 0.431 R☉, a mass of 0.43 M☉, an estimated bolometric luminosity of 0.024 L☉. Stellar evolution modeling indicates an estimated stellar age of 2 Gyr and a metallicity of [Fe/H] = -0.05 dex (near-solar heavy-element abundance). From Earth, LSPM J2116+0234 shines at apparent V-band magnitude 11.961 (faint and requiring research-grade or CCD telescopic photometry) in the Northern 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: Calar Alto Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | LSPM J2116+0234 |
| Spectral Type | M3.0 V |
| Effective Temp (Teff) | 3,475 K |
| Stellar Radius | 0.4310 R☉ |
| Stellar Mass | 0.4300 M☉ |
| Bolometric Luminosity | 0.024 L☉ |
| Metallicity [Fe/H] | -0.050 dex |
| Stellar Age | 2.000 Gyr |
| Apparent Magnitude | V: 11.961 · G: 10.860 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.087600 AU |
| Orbital Period | 14.44 days |
| Mean Orbital Velocity | 66 km/s |
| Orbital Eccentricity (e) | 0.18300 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.44 g/cm³ (21.2 km/s vesc) |
| Insolation Flux | 2.6063 S⊕ (~3,547 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 57.500 LY (17.630 pc) |