TOI-1533 b
Astrophysical Synthesis & Habitability Characterization
TOI-1533 b is a confirmed sub-neptune exoplanet orbiting the star TOI-1533, located approximately 326.3 light-years (100.05 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 0.0974% across the stellar disk), this world measures 2.89 Earth radii and has a measured mass of 28.1 Earth masses. Combining its mass and radius yields a mean bulk density of 6.42 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 3.36 g⊕ (32.95 m/s²), and an escape velocity of 34.9 km/s.
In its orbital architecture around TOI-1533, TOI-1533 b completes one full revolution every 3.646 Earth days at a semi-major axis of 0.0445 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 132.8 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 1011 K (+738°C / +1360°F) and receiving 173.91 S⊕ (~236,689 W/m²), TOI-1533 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-1533 is classified as a stellar host with an effective photospheric temperature of 5,146 K, a radius of 0.849 R☉, a mass of 0.88 M☉, an estimated bolometric luminosity of 0.454 L☉. Stellar evolution modeling indicates an estimated stellar age of 6.9 Gyr and a metallicity of [Fe/H] = 0.24 dex (metal-rich relative to the Sun). From Earth, TOI-1533 shines at apparent V-band magnitude 10.953 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The TOI-1533 system is a multi-planet architecture hosting 2 confirmed worlds, with TOI-1533 b sharing its stellar neighborhood alongside TOI-1533 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 | TOI-1533 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,146 K |
| Stellar Radius | 0.8490 R☉ |
| Stellar Mass | 0.8800 M☉ |
| Bolometric Luminosity | 0.454 L☉ |
| Metallicity [Fe/H] | 0.240 dex |
| Stellar Age | 6.900 Gyr |
| Apparent Magnitude | V: 10.953 · G: 10.682 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.044500 AU |
| Orbital Period | 3.646 days |
| Mean Orbital Velocity | 132.8 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 86.9200° |
| Mean Bulk Density | 6.42 g/cm³ (34.9 km/s vesc) |
| Insolation Flux | 173.9080 S⊕ (~236,689 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 326.300 LY (100.051 pc) |