L 98-59 b
Astrophysical Synthesis & Habitability Characterization
L 98-59 b is a confirmed terrestrial exoplanet orbiting the star L 98-59, located approximately 34.6 light-years (10.62 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 0.0592% across the stellar disk), this world measures 0.837 Earth radii and has a measured mass of 0.46 Earth masses. Combining its mass and radius yields a mean bulk density of 4.33 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 0.66 g⊕ (6.47 m/s²), and an escape velocity of 8.3 km/s.
In its orbital architecture around L 98-59, L 98-59 b completes one full revolution every 2.253 Earth days at a semi-major axis of 0.0223 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 107.7 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.031 (ranging from 0.0216 AU at periapsis to 0.023 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 620 K (+347°C / +657°F) and receiving 24.50 S⊕ (~33,345 W/m²), L 98-59 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star L 98-59 is classified as a low-mass red dwarf of spectral type M3 V with an effective photospheric temperature of 3,415 K, a radius of 0.3155 R☉, a mass of 0.2923 M☉, an estimated bolometric luminosity of 0.012 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.94 Gyr and a metallicity of [Fe/H] = -0.46 dex (metal-poor relative to the Sun). From Earth, L 98-59 shines at apparent V-band magnitude 11.685 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The L 98-59 system is a multi-planet architecture hosting 5 confirmed worlds, with L 98-59 b sharing its stellar neighborhood alongside L 98-59 c, L 98-59 d, L 98-59 e, L 98-59 f.
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 | L 98-59 |
| Spectral Type | M3 V |
| Effective Temp (Teff) | 3,415 K |
| Stellar Radius | 0.3155 R☉ |
| Stellar Mass | 0.2923 M☉ |
| Bolometric Luminosity | 0.012 L☉ |
| Metallicity [Fe/H] | -0.460 dex |
| Stellar Age | 4.940 Gyr |
| Apparent Magnitude | V: 11.685 · G: 10.598 |
| System Architecture | 1 Star, 5 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.022300 AU |
| Orbital Period | 2.253 days |
| Mean Orbital Velocity | 107.7 km/s |
| Orbital Eccentricity (e) | 0.03100 |
| Orbital Inclination (i) | 88.0800° |
| Mean Bulk Density | 4.33 g/cm³ (8.3 km/s vesc) |
| Insolation Flux | 24.5000 S⊕ (~33,345 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 34.600 LY (10.619 pc) |