TOI-824 b
Astrophysical Synthesis & Habitability Characterization
TOI-824 b is a confirmed sub-neptune exoplanet orbiting the star TOI-824, located approximately 208.5 light-years (63.93 parsecs) from the Solar System. First announced in 2020 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.149% across the stellar disk), this world measures 2.926 Earth radii and has a measured mass of 18.467 Earth masses. Combining its mass and radius yields a mean bulk density of 4.06 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 2.16 g⊕ (21.18 m/s²), and an escape velocity of 28.1 km/s.
In its orbital architecture around TOI-824, TOI-824 b completes one full revolution every 1.393 Earth days at a semi-major axis of 0.02177 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 170 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 1253 K (+980°C / +1796°F) and receiving 412.00 S⊕ (~560,732 W/m²), TOI-824 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-824 is classified as an orange K-type star of spectral type K4 V with an effective photospheric temperature of 4,600 K, a radius of 0.695 R☉, a mass of 0.71 M☉, an estimated bolometric luminosity of 0.194 L☉. Stellar evolution modeling indicates an estimated stellar age of 7.5 Gyr and a metallicity of [Fe/H] = -0.092 dex (near-solar heavy-element abundance). From Earth, TOI-824 shines at apparent V-band magnitude 11.314 (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-824 |
| Spectral Type | K4 V |
| Effective Temp (Teff) | 4,600 K |
| Stellar Radius | 0.6950 R☉ |
| Stellar Mass | 0.7100 M☉ |
| Bolometric Luminosity | 0.194 L☉ |
| Metallicity [Fe/H] | -0.092 dex |
| Stellar Age | 7.500 Gyr |
| Apparent Magnitude | V: 11.314 · G: 10.762 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.021770 AU |
| Orbital Period | 1.393 days |
| Mean Orbital Velocity | 170 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 83.6500° |
| Mean Bulk Density | 4.06 g/cm³ (28.1 km/s vesc) |
| Insolation Flux | 412.0000 S⊕ (~560,732 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 208.500 LY (63.926 pc) |