LHS 1903 c
Astrophysical Synthesis & Habitability Characterization
LHS 1903 c is a confirmed sub-neptune exoplanet orbiting the star LHS 1903, located approximately 116.4 light-years (35.69 parsecs) from the Solar System. First announced in 2026 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.1211% across the stellar disk), this world measures 2.046 Earth radii and has a measured mass of 4.55 Earth masses. Combining its mass and radius yields a mean bulk density of 2.93 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.09 g⊕ (10.69 m/s²), and an escape velocity of 16.7 km/s.
In its orbital architecture around LHS 1903, LHS 1903 c completes one full revolution every 6.226 Earth days at a semi-major axis of 0.05387 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 94.1 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.089 carries the world between 0.0491 AU at periapsis and 0.0587 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 559 K (+286°C / +547°F) and receiving 16.20 S⊕ (~22,048 W/m²), LHS 1903 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star LHS 1903 is classified as a low-mass red dwarf of spectral type M with an effective photospheric temperature of 3,664 K, a radius of 0.539 R☉, a mass of 0.538 M☉, an estimated bolometric luminosity of 0.047 L☉. Stellar evolution modeling indicates an estimated stellar age of 7.08 Gyr and a metallicity of [Fe/H] = -0.11 dex (metal-poor relative to the Sun). From Earth, LHS 1903 shines at apparent V-band magnitude 12.23 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The LHS 1903 system is a multi-planet architecture hosting 4 confirmed worlds, with LHS 1903 c sharing its stellar neighborhood alongside LHS 1903 b, LHS 1903 d, LHS 1903 e.
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: Transiting Exoplanet Survey Satellite (TESS) · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | LHS 1903 |
| Spectral Type | M |
| Effective Temp (Teff) | 3,664 K |
| Stellar Radius | 0.5390 R☉ |
| Stellar Mass | 0.5380 M☉ |
| Bolometric Luminosity | 0.047 L☉ |
| Metallicity [Fe/H] | -0.110 dex |
| Stellar Age | 7.080 Gyr |
| Apparent Magnitude | V: 12.230 · G: 11.394 |
| System Architecture | 1 Star, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.053870 AU |
| Orbital Period | 6.226 days |
| Mean Orbital Velocity | 94.1 km/s |
| Orbital Eccentricity (e) | 0.08900 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 2.93 g/cm³ (16.7 km/s vesc) |
| Insolation Flux | 16.2000 S⊕ (~22,048 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 116.400 LY (35.692 pc) |