TOI-663 d
Astrophysical Synthesis & Habitability Characterization
TOI-663 d is a confirmed super-earth exoplanet orbiting the star TOI-663, located approximately 209.5 light-years (64.23 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 0.1182% across the stellar disk), this world measures 1.92 Earth radii and has a measured mass of 5.2 Earth masses. Combining its mass and radius yields a mean bulk density of 4.05 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.41 g⊕ (13.83 m/s²), and an escape velocity of 18.4 km/s.
In its orbital architecture around TOI-663, TOI-663 d completes one full revolution every 7.103 Earth days at a semi-major axis of 0.0576 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 88.2 km/s (compared to Earth's 29.8 km/s).
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 482 K (+209°C / +408°F) and receiving 12.90 S⊕ (~17,557 W/m²), TOI-663 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-663 is classified as a low-mass red dwarf of spectral type M1 V with an effective photospheric temperature of 3,681 K, a radius of 0.512 R☉, a mass of 0.514 M☉, an estimated bolometric luminosity of 0.043 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = 0.07 dex (metal-rich relative to the Sun). From Earth, TOI-663 shines at apparent V-band magnitude 13.667 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The TOI-663 system is a multi-planet architecture hosting 3 confirmed worlds, with TOI-663 d sharing its stellar neighborhood alongside TOI-663 b, TOI-663 c.
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-663 |
| Spectral Type | M1 V |
| Effective Temp (Teff) | 3,681 K |
| Stellar Radius | 0.5120 R☉ |
| Stellar Mass | 0.5140 M☉ |
| Bolometric Luminosity | 0.043 L☉ |
| Metallicity [Fe/H] | 0.070 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 13.667 · G: 12.819 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.057600 AU |
| Orbital Period | 7.103 days |
| Mean Orbital Velocity | 88.2 km/s |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 89.6000° |
| Mean Bulk Density | 4.05 g/cm³ (18.4 km/s vesc) |
| Insolation Flux | 12.9000 S⊕ (~17,557 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 209.500 LY (64.231 pc) |