TOI-5789 e
Astrophysical Synthesis & Habitability Characterization
TOI-5789 e is a confirmed sub-neptune exoplanet orbiting the star TOI-5789, located approximately 66.7 light-years (20.46 parsecs) from the Solar System. First announced in 2026 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 3.43 Earth radii (0.31 Jupiter radii) and has a measured mass of 11.61 Earth masses. Combining its mass and radius yields a mean bulk density of 1.59 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.99 g⊕ (9.71 m/s²), and an escape velocity of 20.6 km/s.
In its orbital architecture around TOI-5789, TOI-5789 e completes one full revolution every 62.98 Earth days at a semi-major axis of 0.2901 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 50.1 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.071 carries the world between 0.2695 AU at periapsis and 0.3107 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 424 K (+151°C / +304°F) and receiving 5.57 S⊕ (~7,585 W/m²), TOI-5789 e orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-5789 is classified as an orange K-type star of spectral type K1 V with an effective photospheric temperature of 5,185 K, a radius of 0.833 R☉, a mass of 0.821 M☉, an estimated bolometric luminosity of 0.45 L☉. Stellar evolution modeling indicates an estimated stellar age of 9.4 Gyr and a metallicity of [Fe/H] = -0.12 dex (metal-poor relative to the Sun). From Earth, TOI-5789 shines at apparent V-band magnitude 7.351 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The TOI-5789 system is a multi-planet architecture hosting 4 confirmed worlds, with TOI-5789 e sharing its stellar neighborhood alongside TOI-5789 b, TOI-5789 c, TOI-5789 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: Multiple Observatories · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | TOI-5789 |
| Spectral Type | K1 V |
| Effective Temp (Teff) | 5,185 K |
| Stellar Radius | 0.8330 R☉ |
| Stellar Mass | 0.8210 M☉ |
| Bolometric Luminosity | 0.45 L☉ |
| Metallicity [Fe/H] | -0.120 dex |
| Stellar Age | 9.400 Gyr |
| Apparent Magnitude | V: 7.351 · G: 7.100 |
| System Architecture | 1 Star, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.290100 AU |
| Orbital Period | 62.98 days |
| Mean Orbital Velocity | 50.1 km/s |
| Orbital Eccentricity (e) | 0.07100 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 1.59 g/cm³ (20.6 km/s vesc) |
| Insolation Flux | 5.5729 S⊕ (~7,585 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 66.700 LY (20.458 pc) |