TOI-238 c
Astrophysical Synthesis & Habitability Characterization
TOI-238 c is a confirmed sub-neptune exoplanet orbiting the star TOI-238, located approximately 262.7 light-years (80.54 parsecs) from the Solar System. First announced in 2024 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 2.18 Earth radii and has a measured mass of 6.7 Earth masses. Combining its mass and radius yields a mean bulk density of 3.57 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.41 g⊕ (13.83 m/s²), and an escape velocity of 19.6 km/s.
In its orbital architecture around TOI-238, TOI-238 c completes one full revolution every 8.466 Earth days at a semi-major axis of 0.0749 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 96.3 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.36, swinging from 0.0479 AU at periapsis out to 0.1019 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 696 K (+423°C / +793°F) and receiving 58.30 S⊕ (~79,346 W/m²), TOI-238 c 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 K2V with an effective photospheric temperature of 5,059 K, a radius of 0.733 R☉, a mass of 0.79 M☉, an estimated bolometric luminosity of 0.316 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.3 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 c sharing its stellar neighborhood alongside TOI-238 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: Multiple Observatories · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | TOI-238 |
| Spectral Type | K2V |
| Effective Temp (Teff) | 5,059 K |
| Stellar Radius | 0.7330 R☉ |
| Stellar Mass | 0.7900 M☉ |
| Bolometric Luminosity | 0.316 L☉ |
| Metallicity [Fe/H] | -0.114 dex |
| Stellar Age | 4.300 Gyr |
| Apparent Magnitude | V: 10.748 · G: 10.488 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.074900 AU |
| Orbital Period | 8.466 days |
| Mean Orbital Velocity | 96.3 km/s |
| Orbital Eccentricity (e) | 0.36000 |
| Orbital Inclination (i) | 87.9380° |
| Mean Bulk Density | 3.57 g/cm³ (19.6 km/s vesc) |
| Insolation Flux | 58.3000 S⊕ (~79,346 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 262.700 LY (80.541 pc) |