TOI-1438 b
Astrophysical Synthesis & Habitability Characterization
TOI-1438 b is a confirmed sub-neptune exoplanet orbiting the star TOI-1438, located approximately 360.4 light-years (110.51 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 0.1155% across the stellar disk), this world measures 3.04 Earth radii (0.27 Jupiter radii) and has a measured mass of 9.4 Earth masses. Combining its mass and radius yields a mean bulk density of 1.84 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.02 g⊕ (10 m/s²), and an escape velocity of 19.7 km/s.
In its orbital architecture around TOI-1438, TOI-1438 b completes one full revolution every 5.14 Earth days at a semi-major axis of 0.0553 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 117.1 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 971 K (+698°C / +1288°F) and receiving 145.00 S⊕ (~197,345 W/m²), TOI-1438 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-1438 is classified as an orange K-type star of spectral type K0 V with an effective photospheric temperature of 5,230 K, a radius of 0.82 R☉, a mass of 0.876 M☉, an estimated bolometric luminosity of 0.451 L☉. Stellar evolution modeling indicates an estimated stellar age of 2.2 Gyr and a metallicity of [Fe/H] = 0.03 dex (near-solar heavy-element abundance). From Earth, TOI-1438 shines at apparent V-band magnitude 10.957 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The TOI-1438 system is a multi-planet architecture hosting 2 confirmed worlds, with TOI-1438 b sharing its stellar neighborhood alongside TOI-1438 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-1438 |
| Spectral Type | K0 V |
| Effective Temp (Teff) | 5,230 K |
| Stellar Radius | 0.8200 R☉ |
| Stellar Mass | 0.8760 M☉ |
| Bolometric Luminosity | 0.451 L☉ |
| Metallicity [Fe/H] | 0.030 dex |
| Stellar Age | 2.200 Gyr |
| Apparent Magnitude | V: 10.957 · G: 10.855 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.055300 AU |
| Orbital Period | 5.14 days |
| Mean Orbital Velocity | 117.1 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 86.2100° |
| Mean Bulk Density | 1.84 g/cm³ (19.7 km/s vesc) |
| Insolation Flux | 145.0000 S⊕ (~197,345 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 360.400 LY (110.513 pc) |