TOI-558 b
Astrophysical Synthesis & Habitability Characterization
TOI-558 b is a confirmed gas giant exoplanet orbiting the star TOI-558, located approximately 1313.2 light-years (402.63 parsecs) from the Solar System. First announced in 2021 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.5565% across the stellar disk), this world measures 12.173 Earth radii (1.09 Jupiter radii) and has a measured mass of 1147.361 Earth masses (3.61 Jupiter masses). Combining its mass and radius yields a mean bulk density of 3.51 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 7.74 g⊕ (75.9 m/s²), and an escape velocity of 108.6 km/s.
In its orbital architecture around TOI-558, TOI-558 b completes one full revolution every 14.574 Earth days at a semi-major axis of 0.1291 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 96.4 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.298, swinging from 0.0906 AU at periapsis out to 0.1676 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1061 K (+788°C / +1450°F) and receiving 248.86 S⊕ (~338,692 W/m²), TOI-558 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-558 is classified as a warm F-type star of spectral type F V with an effective photospheric temperature of 6,466 K, a radius of 1.496 R☉, a mass of 1.349 M☉, an estimated bolometric luminosity of 3.51 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.79 Gyr and a metallicity of [Fe/H] = -0.004 dex (near-solar heavy-element abundance). From Earth, TOI-558 shines at apparent V-band magnitude 11.233 (faint and requiring research-grade or CCD telescopic photometry) in the Southern 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: Transiting Exoplanet Survey Satellite (TESS) · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | TOI-558 |
| Spectral Type | F V |
| Effective Temp (Teff) | 6,466 K |
| Stellar Radius | 1.4960 R☉ |
| Stellar Mass | 1.3490 M☉ |
| Bolometric Luminosity | 3.51 L☉ |
| Metallicity [Fe/H] | -0.004 dex |
| Stellar Age | 1.790 Gyr |
| Apparent Magnitude | V: 11.233 · G: 11.325 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.129100 AU |
| Orbital Period | 14.574 days |
| Mean Orbital Velocity | 96.4 km/s |
| Orbital Eccentricity (e) | 0.29800 |
| Orbital Inclination (i) | 86.2400° |
| Mean Bulk Density | 3.51 g/cm³ (108.6 km/s vesc) |
| Insolation Flux | 248.8554 S⊕ (~338,692 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1313.200 LY (402.630 pc) |