TOI-1266 d
Astrophysical Synthesis & Habitability Characterization
TOI-1266 d is a confirmed super-earth exoplanet orbiting the star TOI-1266, located approximately 117.5 light-years (36.01 parsecs) from the Solar System. First announced in 2025 by Transiting Exoplanet Survey Satellite (TESS) using the Transit Timing Variations detection technique (producing an estimated primary transit depth of 0.1421% across the stellar disk), this world measures 1.74 Earth radii and has a measured mass of 3.68 Earth masses. Combining its mass and radius yields a mean bulk density of 3.85 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.22 g⊕ (11.96 m/s²), and an escape velocity of 16.3 km/s.
In its orbital architecture around TOI-1266, TOI-1266 d completes one full revolution every 32.509 Earth days at a semi-major axis of 0.1513 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 50.6 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.087 carries the world between 0.1381 AU at periapsis and 0.1645 AU at apoapsis, driving measurable seasonal insolation cycles.
✓ Classified as a Temperate Habitable Zone Candidate.
With an estimated equilibrium temperature of 288 K (+15°C / +59°F) and an incident stellar irradiance of 1.30 S⊕ (~1,769 W/m²), TOI-1266 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-1266 is classified as a low-mass red dwarf of spectral type M2 with an effective photospheric temperature of 3,563 K, a radius of 0.4232 R☉, a mass of 0.437 M☉, an estimated bolometric luminosity of 0.026 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.6 Gyr and a metallicity of [Fe/H] = -0.109 dex (metal-poor relative to the Sun). From Earth, TOI-1266 shines at apparent V-band magnitude 12.941 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The TOI-1266 system is a multi-planet architecture hosting 3 confirmed worlds, with TOI-1266 d sharing its stellar neighborhood alongside TOI-1266 b, TOI-1266 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-1266 |
| Spectral Type | M2 |
| Effective Temp (Teff) | 3,563 K |
| Stellar Radius | 0.4232 R☉ |
| Stellar Mass | 0.4370 M☉ |
| Bolometric Luminosity | 0.026 L☉ |
| Metallicity [Fe/H] | -0.109 dex |
| Stellar Age | 4.600 Gyr |
| Apparent Magnitude | V: 12.941 · G: 12.122 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.151300 AU |
| Orbital Period | 32.509 days |
| Mean Orbital Velocity | 50.6 km/s |
| Orbital Eccentricity (e) | 0.08700 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 3.85 g/cm³ (16.3 km/s vesc) |
| Insolation Flux | 1.3000 S⊕ (~1,769 W/m²) |
| Habitable Zone Status | ★ Temperate Zone |
| Celestial Distance | 117.500 LY (36.012 pc) |