TOI-756 b
Astrophysical Synthesis & Habitability Characterization
TOI-756 b is a confirmed sub-neptune exoplanet orbiting the star TOI-756, located approximately 281.1 light-years (86.18 parsecs) from the Solar System. First announced in 2025 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.2602% across the stellar disk), this world measures 2.81 Earth radii and has a measured mass of 9.83 Earth masses. Combining its mass and radius yields a mean bulk density of 2.44 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.24 g⊕ (12.16 m/s²), and an escape velocity of 20.9 km/s.
In its orbital architecture around TOI-756, TOI-756 b completes one full revolution every 1.239 Earth days at a semi-major axis of 0.018 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 158 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 934 K (+661°C / +1222°F) and receiving 127.00 S⊕ (~172,847 W/m²), TOI-756 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-756 is classified as a low-mass red dwarf of spectral type M1 V with an effective photospheric temperature of 3,657 K, a radius of 0.505 R☉, a mass of 0.505 M☉, an estimated bolometric luminosity of 0.041 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.2 Gyr and a metallicity of [Fe/H] = 0.196 dex (metal-rich relative to the Sun). From Earth, TOI-756 shines at apparent V-band magnitude 14.607 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The TOI-756 system is a multi-planet architecture hosting 2 confirmed worlds, with TOI-756 b sharing its stellar neighborhood alongside TOI-756 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-756 |
| Spectral Type | M1 V |
| Effective Temp (Teff) | 3,657 K |
| Stellar Radius | 0.5050 R☉ |
| Stellar Mass | 0.5050 M☉ |
| Bolometric Luminosity | 0.041 L☉ |
| Metallicity [Fe/H] | 0.196 dex |
| Stellar Age | 3.200 Gyr |
| Apparent Magnitude | V: 14.607 · G: 13.696 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.018000 AU |
| Orbital Period | 1.239 days |
| Mean Orbital Velocity | 158 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 85.5300° |
| Mean Bulk Density | 2.44 g/cm³ (20.9 km/s vesc) |
| Insolation Flux | 127.0000 S⊕ (~172,847 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 281.100 LY (86.176 pc) |