LHS 1903 d
Astrophysical Synthesis & Habitability Characterization
LHS 1903 d 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 0.1808% across the stellar disk), this world measures 2.5 Earth radii and has a measured mass of 5.96 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 0.95 g⊕ (9.32 m/s²), and an escape velocity of 17.3 km/s.
In its orbital architecture around LHS 1903, LHS 1903 d completes one full revolution every 12.566 Earth days at a semi-major axis of 0.08604 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 74.5 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.112 carries the world between 0.0764 AU at periapsis and 0.0957 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 442 K (+169°C / +336°F) and receiving 6.35 S⊕ (~8,642 W/m²), LHS 1903 d 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 d sharing its stellar neighborhood alongside LHS 1903 b, LHS 1903 c, 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) | 0.086040 AU |
| Orbital Period | 12.566 days |
| Mean Orbital Velocity | 74.5 km/s |
| Orbital Eccentricity (e) | 0.11200 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 2.1 g/cm³ (17.3 km/s vesc) |
| Insolation Flux | 6.3500 S⊕ (~8,642 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 116.400 LY (35.692 pc) |