TOI-1238 c
Astrophysical Synthesis & Habitability Characterization
TOI-1238 c is a confirmed sub-neptune exoplanet orbiting the star TOI-1238, located approximately 230.6 light-years (70.72 parsecs) from the Solar System. First announced in 2022 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.1112% across the stellar disk), this world measures 2.11 Earth radii and has a measured mass of 8.32 Earth masses. Combining its mass and radius yields a mean bulk density of 4.88 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.87 g⊕ (18.34 m/s²), and an escape velocity of 22.2 km/s.
In its orbital architecture around TOI-1238, TOI-1238 c completes one full revolution every 3.295 Earth days at a semi-major axis of 0.037 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 122.2 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.15 carries the world between 0.0315 AU at periapsis and 0.0426 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 695 K (+422°C / +792°F) and receiving 63.00 S⊕ (~85,743 W/m²), TOI-1238 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-1238 is classified as an orange K-type star of spectral type K7/M0 with an effective photospheric temperature of 4,089 K, a radius of 0.58 R☉, a mass of 0.59 M☉, an estimated bolometric luminosity of 0.084 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.8 Gyr and a metallicity of [Fe/H] = 0.31 dex (metal-rich relative to the Sun). From Earth, TOI-1238 shines at apparent V-band magnitude 12.796 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The TOI-1238 system is a multi-planet architecture hosting 2 confirmed worlds, with TOI-1238 c sharing its stellar neighborhood alongside TOI-1238 b.
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-1238 |
| Spectral Type | K7/M0 |
| Effective Temp (Teff) | 4,089 K |
| Stellar Radius | 0.5800 R☉ |
| Stellar Mass | 0.5900 M☉ |
| Bolometric Luminosity | 0.084 L☉ |
| Metallicity [Fe/H] | 0.310 dex |
| Stellar Age | 0.800 Gyr |
| Apparent Magnitude | V: 12.796 · G: 12.222 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.037000 AU |
| Orbital Period | 3.295 days |
| Mean Orbital Velocity | 122.2 km/s |
| Orbital Eccentricity (e) | 0.15000 |
| Orbital Inclination (i) | 88.3800° |
| Mean Bulk Density | 4.88 g/cm³ (22.2 km/s vesc) |
| Insolation Flux | 63.0000 S⊕ (~85,743 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 230.600 LY (70.715 pc) |