TOI-451 d
Astrophysical Synthesis & Habitability Characterization
TOI-451 d is a confirmed sub-neptune exoplanet orbiting the star TOI-451, located approximately 403.6 light-years (123.74 parsecs) from the Solar System. First announced in 2020 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.1797% across the stellar disk), this world measures 3.93 Earth radii (0.35 Jupiter radii) and has a measured mass of 10.2 Earth masses. Combining its mass and radius yields a mean bulk density of 0.93 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.66 g⊕ (6.47 m/s²), and an escape velocity of 18 km/s.
In its orbital architecture around TOI-451, TOI-451 d completes one full revolution every 16.365 Earth days at a semi-major axis of 0.1168 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 77.6 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 714 K (+441°C / +826°F) and receiving 43.20 S⊕ (~58,795 W/m²), TOI-451 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-451 is classified as a solar-type yellow star of spectral type G8 V with an effective photospheric temperature of 5,490 K, a radius of 0.85 R☉, a mass of 0.93 M☉, an estimated bolometric luminosity of 0.589 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.125 Gyr and a metallicity of [Fe/H] = 0.02 dex (near-solar heavy-element abundance). From Earth, TOI-451 shines at apparent V-band magnitude 10.939 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The TOI-451 system is a multi-planet architecture hosting 3 confirmed worlds, with TOI-451 d sharing its stellar neighborhood alongside TOI-451 b, TOI-451 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-451 |
| Spectral Type | G8 V |
| Effective Temp (Teff) | 5,490 K |
| Stellar Radius | 0.8500 R☉ |
| Stellar Mass | 0.9300 M☉ |
| Bolometric Luminosity | 0.589 L☉ |
| Metallicity [Fe/H] | 0.020 dex |
| Stellar Age | 0.125 Gyr |
| Apparent Magnitude | V: 10.939 · G: 10.750 |
| System Architecture | 2 Stars, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.116800 AU |
| Orbital Period | 16.365 days |
| Mean Orbital Velocity | 77.6 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.2600° |
| Mean Bulk Density | 0.93 g/cm³ (18 km/s vesc) |
| Insolation Flux | 43.2000 S⊕ (~58,795 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 403.600 LY (123.739 pc) |