TOI-238 b
Astrophysical Synthesis & Habitability Characterization
TOI-238 b is a confirmed super-earth exoplanet orbiting the star TOI-238, located approximately 262.7 light-years (80.54 parsecs) from the Solar System. First announced in 2024 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.0357% across the stellar disk), this world measures 1.559 Earth radii and has a measured mass of 3.37 Earth masses. Combining its mass and radius yields a mean bulk density of 4.9 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.39 g⊕ (13.63 m/s²), and an escape velocity of 16.4 km/s.
In its orbital architecture around TOI-238, TOI-238 b completes one full revolution every 1.273 Earth days at a semi-major axis of 0.0212 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 181.2 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.18 carries the world between 0.0174 AU at periapsis and 0.025 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1378 K (+1105°C / +2021°F) and receiving 753.10 S⊕ (~1,024,969 W/m²), TOI-238 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-238 is classified as an orange K-type star of spectral type K2 V with an effective photospheric temperature of 5,059 K, a radius of 0.756 R☉, a mass of 0.781 M☉, an estimated bolometric luminosity of 0.336 L☉. Stellar evolution modeling indicates an estimated stellar age of 7.9 Gyr and a metallicity of [Fe/H] = -0.114 dex (metal-poor relative to the Sun). From Earth, TOI-238 shines at apparent V-band magnitude 10.748 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The TOI-238 system is a multi-planet architecture hosting 2 confirmed worlds, with TOI-238 b sharing its stellar neighborhood alongside TOI-238 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-238 |
| Spectral Type | K2 V |
| Effective Temp (Teff) | 5,059 K |
| Stellar Radius | 0.7560 R☉ |
| Stellar Mass | 0.7810 M☉ |
| Bolometric Luminosity | 0.336 L☉ |
| Metallicity [Fe/H] | -0.114 dex |
| Stellar Age | 7.900 Gyr |
| Apparent Magnitude | V: 10.748 · G: 10.488 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.021200 AU |
| Orbital Period | 1.273 days |
| Mean Orbital Velocity | 181.2 km/s |
| Orbital Eccentricity (e) | 0.18000 |
| Orbital Inclination (i) | 85.7800° |
| Mean Bulk Density | 4.9 g/cm³ (16.4 km/s vesc) |
| Insolation Flux | 753.1000 S⊕ (~1,024,969 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 262.700 LY (80.541 pc) |