TOI-620 b
Astrophysical Synthesis & Habitability Characterization
TOI-620 b is a confirmed sub-neptune exoplanet orbiting the star TOI-620, located approximately 107.7 light-years (33.02 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 0.3928% across the stellar disk), this world measures 3.76 Earth radii (0.34 Jupiter radii) and has a measured mass of 13.6 Earth masses. Combining its mass and radius yields a mean bulk density of 1.41 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.96 g⊕ (9.41 m/s²), and an escape velocity of 21.3 km/s.
In its orbital architecture around TOI-620, TOI-620 b completes one full revolution every 5.099 Earth days at a semi-major axis of 0.04825 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 102.9 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.22 carries the world between 0.0376 AU at periapsis and 0.0589 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 604 K (+331°C / +628°F) and receiving 20.80 S⊕ (~28,309 W/m²), TOI-620 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-620 is classified as a low-mass red dwarf of spectral type M2.5 V with an effective photospheric temperature of 3,708 K, a radius of 0.55 R☉, a mass of 0.577 M☉, an estimated bolometric luminosity of 0.051 L☉. Stellar evolution modeling indicates an estimated stellar age of 7.2 Gyr and a metallicity of [Fe/H] = 0.35 dex (metal-rich relative to the Sun). From Earth, TOI-620 shines at apparent V-band magnitude 12.262 (faint and requiring research-grade or CCD telescopic photometry) in the Southern 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-620 |
| Spectral Type | M2.5 V |
| Effective Temp (Teff) | 3,708 K |
| Stellar Radius | 0.5500 R☉ |
| Stellar Mass | 0.5770 M☉ |
| Bolometric Luminosity | 0.051 L☉ |
| Metallicity [Fe/H] | 0.350 dex |
| Stellar Age | 7.200 Gyr |
| Apparent Magnitude | V: 12.262 · G: 11.310 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.048250 AU |
| Orbital Period | 5.099 days |
| Mean Orbital Velocity | 102.9 km/s |
| Orbital Eccentricity (e) | 0.22000 |
| Orbital Inclination (i) | 87.4700° |
| Mean Bulk Density | 1.41 g/cm³ (21.3 km/s vesc) |
| Insolation Flux | 20.8000 S⊕ (~28,309 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 107.700 LY (33.023 pc) |