TOI-700 d
Astrophysical Synthesis & Habitability Characterization
TOI-700 d is a confirmed terrestrial exoplanet orbiting the star TOI-700, located approximately 101.5 light-years (31.13 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 0.0654% across the stellar disk), this world measures 1.145 Earth radii and has a measured mass of 1.58 Earth masses. Combining its mass and radius yields a mean bulk density of 5.8 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.21 g⊕ (11.87 m/s²), and an escape velocity of 13.1 km/s.
In its orbital architecture around TOI-700, TOI-700 d completes one full revolution every 37.423 Earth days at a semi-major axis of 0.1642 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 47.7 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.042 (ranging from 0.1573 AU at periapsis to 0.1711 AU at apoapsis), the planet experiences minimal orbital distance variation.
✓ Classified as a Temperate Habitable Zone Candidate.
With an estimated equilibrium temperature of 269 K (-4°C / +25°F) and an incident stellar irradiance of 0.85 S⊕ (~1,157 W/m²), TOI-700 d orbits within the empirical circumstellar habitable zone where a rocky surface under sufficient atmospheric pressure can maintain liquid surface water.
The host star TOI-700 is classified as a low-mass red dwarf of spectral type M2.5 V with an effective photospheric temperature of 3,459 K, a radius of 0.4104 R☉, a mass of 0.417 M☉, an estimated bolometric luminosity of 0.022 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.5 Gyr and a metallicity of [Fe/H] = -0.07 dex (near-solar heavy-element abundance). From Earth, TOI-700 shines at apparent V-band magnitude 13.151 (faint and requiring research-grade or CCD telescopic photometry) in the Southern celestial hemisphere. The TOI-700 system is a multi-planet architecture hosting 4 confirmed worlds, with TOI-700 d sharing its stellar neighborhood alongside TOI-700 b, TOI-700 c, TOI-700 e.
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-700 |
| Spectral Type | M2.5 V |
| Effective Temp (Teff) | 3,459 K |
| Stellar Radius | 0.4104 R☉ |
| Stellar Mass | 0.4170 M☉ |
| Bolometric Luminosity | 0.022 L☉ |
| Metallicity [Fe/H] | -0.070 dex |
| Stellar Age | 1.500 Gyr |
| Apparent Magnitude | V: 13.151 · G: 12.067 |
| System Architecture | 1 Star, 4 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.164200 AU |
| Orbital Period | 37.423 days |
| Mean Orbital Velocity | 47.7 km/s |
| Orbital Eccentricity (e) | 0.04200 |
| Orbital Inclination (i) | 89.8300° |
| Mean Bulk Density | 5.8 g/cm³ (13.1 km/s vesc) |
| Insolation Flux | 0.8500 S⊕ (~1,157 W/m²) |
| Habitable Zone Status | ★ Temperate Zone |
| Celestial Distance | 101.500 LY (31.127 pc) |