LP 791-18 b
Astrophysical Synthesis & Habitability Characterization
LP 791-18 b is a confirmed terrestrial exoplanet orbiting the star LP 791-18, located approximately 86.4 light-years (26.49 parsecs) from the Solar System. First announced in 2019 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.3727% across the stellar disk), this world measures 1.212 Earth radii and has a measured mass of 1.94 Earth masses. Combining its mass and radius yields a mean bulk density of 6.01 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.32 g⊕ (12.94 m/s²), and an escape velocity of 14.2 km/s.
In its orbital architecture around LP 791-18, LP 791-18 b completes one full revolution every 0.948 Earth days at a semi-major axis of 0.00978 AU (an ultra-close orbit less than one-seventh of Mercury's 0.387 AU distance from the Sun, where strong stellar tidal forces typically induce synchronous rotation). Its mean orbital velocity is approximately 112.2 km/s (compared to Earth's 29.8 km/s). The orbit is modeled as circular (e = 0.00), maintaining a constant stellar distance throughout its year.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 564 K (+291°C / +556°F) and receiving 24.14 S⊕ (~32,855 W/m²), LP 791-18 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star LP 791-18 is classified as a low-mass red dwarf of spectral type M(6.1 +/- 0.7) V with an effective photospheric temperature of 2,960 K, a radius of 0.182 R☉, a mass of 0.139 M☉, an estimated bolometric luminosity of 0.00228 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.5 Gyr and a metallicity of [Fe/H] = -0.09 dex (near-solar heavy-element abundance). From Earth, LP 791-18 shines at apparent V-band magnitude 16.91 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The LP 791-18 system is a multi-planet architecture hosting 3 confirmed worlds, with LP 791-18 b sharing its stellar neighborhood alongside LP 791-18 d, LP 791-18 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: Transiting Exoplanet Survey Satellite (TESS) · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | LP 791-18 |
| Spectral Type | M(6.1 +/- 0.7) V |
| Effective Temp (Teff) | 2,960 K |
| Stellar Radius | 0.1820 R☉ |
| Stellar Mass | 0.1390 M☉ |
| Bolometric Luminosity | 0.00228 L☉ |
| Metallicity [Fe/H] | -0.090 dex |
| Stellar Age | 0.500 Gyr |
| Apparent Magnitude | V: 16.910 · G: 15.072 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.009780 AU |
| Orbital Period | 0.948 days |
| Mean Orbital Velocity | 112.2 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 88.3700° |
| Mean Bulk Density | 6.01 g/cm³ (14.2 km/s vesc) |
| Insolation Flux | 24.1400 S⊕ (~32,855 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 86.400 LY (26.493 pc) |