TOI-2120 b
Astrophysical Synthesis & Habitability Characterization
TOI-2120 b is a confirmed sub-neptune exoplanet orbiting the star TOI-2120, located approximately 104.9 light-years (32.18 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 0.6305% across the stellar disk), this world measures 2.122 Earth radii and has a measured mass of 6.8 Earth masses. Combining its mass and radius yields a mean bulk density of 3.92 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.51 g⊕ (14.81 m/s²), and an escape velocity of 20 km/s.
In its orbital architecture around TOI-2120, TOI-2120 b completes one full revolution every 5.8 Earth days at a semi-major axis of 0.0377 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 70.7 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.32, swinging from 0.0256 AU at periapsis out to 0.0498 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 384 K (+111°C / +232°F) and receiving 3.61 S⊕ (~4,913 W/m²), TOI-2120 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-2120 is classified as a stellar host with an effective photospheric temperature of 3,131 K, a radius of 0.245 R☉, a mass of 0.211 M☉, an estimated bolometric luminosity of 0.00518 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.39 dex (metal-rich relative to the Sun). From Earth, TOI-2120 shines at apparent V-band magnitude 15.648 (faint and requiring research-grade or CCD telescopic photometry) in the Northern 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-2120 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 3,131 K |
| Stellar Radius | 0.2450 R☉ |
| Stellar Mass | 0.2110 M☉ |
| Bolometric Luminosity | 0.00518 L☉ |
| Metallicity [Fe/H] | 0.390 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 15.648 · G: 14.187 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.037700 AU |
| Orbital Period | 5.8 days |
| Mean Orbital Velocity | 70.7 km/s |
| Orbital Eccentricity (e) | 0.32000 |
| Orbital Inclination (i) | 88.6700° |
| Mean Bulk Density | 3.92 g/cm³ (20 km/s vesc) |
| Insolation Flux | 3.6100 S⊕ (~4,913 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 104.900 LY (32.176 pc) |