TOI-5543 b
Astrophysical Synthesis & Habitability Characterization
TOI-5543 b is a confirmed sub-neptune exoplanet orbiting the star TOI-5543, located approximately 408.3 light-years (125.19 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 0.1649% across the stellar disk), this world measures 3.78 Earth radii (0.34 Jupiter radii) and has a measured mass of 13.7 Earth masses. Combining its mass and radius yields a mean bulk density of 1.4 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.96 g⊕ (9.41 m/s²), and an escape velocity of 21.3 km/s.
In its orbital architecture around TOI-5543, TOI-5543 b completes one full revolution every 3.542 Earth days. 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 994 K (+721°C / +1330°F) and receiving 230.73 S⊕ (~314,026 W/m²), TOI-5543 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-5543 is classified as a stellar host with an effective photospheric temperature of 5,058 K, a radius of 0.8533 R☉, a mass of 0.845 M☉, an estimated bolometric luminosity of 0.428 L☉. From Earth, TOI-5543 shines at apparent V-band magnitude 11.565 (faint and requiring research-grade or CCD telescopic photometry) in the Northern 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-5543 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,058 K |
| Stellar Radius | 0.8533 R☉ |
| Stellar Mass | 0.8450 M☉ |
| Bolometric Luminosity | 0.428 L☉ |
| Metallicity [Fe/H] | — |
| Stellar Age | — |
| Apparent Magnitude | V: 11.565 · G: 11.226 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | — |
| Orbital Period | 3.542 days |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.4 g/cm³ (21.3 km/s vesc) |
| Insolation Flux | 230.7315 S⊕ (~314,026 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 408.300 LY (125.194 pc) |