TOI-789 b
Astrophysical Synthesis & Habitability Characterization
TOI-789 b is a confirmed terrestrial exoplanet orbiting the star TOI-789, located approximately 141.6 light-years (43.41 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 0.085% across the stellar disk), this world measures 1.18 Earth radii and has a measured mass of 3.7 Earth masses. Combining its mass and radius yields a mean bulk density of 12.42 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 2.66 g⊕ (26.09 m/s²), and an escape velocity of 19.8 km/s.
In its orbital architecture around TOI-789, TOI-789 b completes one full revolution every 5.447 Earth days at a semi-major axis of 0.043 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 85.9 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.05 carries the world between 0.0409 AU at periapsis and 0.0451 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 448 K (+175°C / +347°F) and receiving 9.50 S⊕ (~12,930 W/m²), TOI-789 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-789 is classified as a low-mass red dwarf of spectral type M3 V with an effective photospheric temperature of 3,471 K, a radius of 0.371 R☉, a mass of 0.358 M☉, an estimated bolometric luminosity of 0.018 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0 dex (near-solar heavy-element abundance). From Earth, TOI-789 shines at apparent V-band magnitude 14.23 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The TOI-789 system is a multi-planet architecture hosting 3 confirmed worlds, with TOI-789 b sharing its stellar neighborhood alongside TOI-789 c, TOI-789 d.
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-789 |
| Spectral Type | M3 V |
| Effective Temp (Teff) | 3,471 K |
| Stellar Radius | 0.3710 R☉ |
| Stellar Mass | 0.3580 M☉ |
| Bolometric Luminosity | 0.018 L☉ |
| Metallicity [Fe/H] | 0.000 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 14.230 · G: 13.164 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.043000 AU |
| Orbital Period | 5.447 days |
| Mean Orbital Velocity | 85.9 km/s |
| Orbital Eccentricity (e) | 0.05000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 12.42 g/cm³ (19.8 km/s vesc) |
| Insolation Flux | 9.5000 S⊕ (~12,930 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 141.600 LY (43.407 pc) |