TOI-444 b
Astrophysical Synthesis & Habitability Characterization
TOI-444 b is a confirmed sub-neptune exoplanet orbiting the star TOI-444, located approximately 187.2 light-years (57.4 parsecs) from the Solar System. First announced in 2023 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.1063% across the stellar disk), this world measures 2.77 Earth radii and has a measured mass of 8.1 Earth masses. Combining its mass and radius yields a mean bulk density of 2.1 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.06 g⊕ (10.4 m/s²), and an escape velocity of 19.1 km/s.
In its orbital architecture around TOI-444, TOI-444 b completes one full revolution every 17.964 Earth days at a semi-major axis of 0.133 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 80.5 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 609 K (+336°C / +637°F) and receiving 23.47 S⊕ (~31,942 W/m²), TOI-444 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-444 is classified as an orange K-type star of spectral type K1/2 V with an effective photospheric temperature of 5,225 K, a radius of 0.779 R☉, a mass of 0.96 M☉, an estimated bolometric luminosity of 0.406 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.57 Gyr and a metallicity of [Fe/H] = 0.08 dex (metal-rich relative to the Sun). From Earth, TOI-444 shines at apparent V-band magnitude 9.86 (accessible to binoculars and small amateur telescopes) in the Southern celestial hemisphere.
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-444 |
| Spectral Type | K1/2 V |
| Effective Temp (Teff) | 5,225 K |
| Stellar Radius | 0.7790 R☉ |
| Stellar Mass | 0.9600 M☉ |
| Bolometric Luminosity | 0.406 L☉ |
| Metallicity [Fe/H] | 0.080 dex |
| Stellar Age | 0.570 Gyr |
| Apparent Magnitude | V: 9.860 · G: 9.606 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.133000 AU |
| Orbital Period | 17.964 days |
| Mean Orbital Velocity | 80.5 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 89.6470° |
| Mean Bulk Density | 2.1 g/cm³ (19.1 km/s vesc) |
| Insolation Flux | 23.4694 S⊕ (~31,942 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 187.200 LY (57.397 pc) |