TOI-1749 d
Astrophysical Synthesis & Habitability Characterization
TOI-1749 d is a confirmed sub-neptune exoplanet orbiting the star TOI-1749, located approximately 324.7 light-years (99.56 parsecs) from the Solar System. First announced in 2021 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.1764% across the stellar disk), this world measures 2.52 Earth radii and has a measured mass of 15 Earth masses. Combining its mass and radius yields a mean bulk density of 5.17 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 2.36 g⊕ (23.14 m/s²), and an escape velocity of 27.3 km/s.
In its orbital architecture around TOI-1749, TOI-1749 d completes one full revolution every 9.05 Earth days at a semi-major axis of 0.0707 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 85 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.062 carries the world between 0.0663 AU at periapsis and 0.0751 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 533 K (+260°C / +500°F) and receiving 14.21 S⊕ (~19,336 W/m²), TOI-1749 d orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-1749 is classified as a low-mass red dwarf of spectral type M0 V with an effective photospheric temperature of 3,985 K, a radius of 0.55 R☉, a mass of 0.58 M☉, an estimated bolometric luminosity of 0.068 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.8 Gyr and a metallicity of [Fe/H] = -0.26 dex (metal-poor relative to the Sun). From Earth, TOI-1749 shines at apparent V-band magnitude 13.86 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The TOI-1749 system is a multi-planet architecture hosting 3 confirmed worlds, with TOI-1749 d sharing its stellar neighborhood alongside TOI-1749 b, TOI-1749 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-1749 |
| Spectral Type | M0 V |
| Effective Temp (Teff) | 3,985 K |
| Stellar Radius | 0.5500 R☉ |
| Stellar Mass | 0.5800 M☉ |
| Bolometric Luminosity | 0.068 L☉ |
| Metallicity [Fe/H] | -0.260 dex |
| Stellar Age | 0.800 Gyr |
| Apparent Magnitude | V: 13.860 · G: 13.180 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.070700 AU |
| Orbital Period | 9.05 days |
| Mean Orbital Velocity | 85 km/s |
| Orbital Eccentricity (e) | 0.06200 |
| Orbital Inclination (i) | 88.5300° |
| Mean Bulk Density | 5.17 g/cm³ (27.3 km/s vesc) |
| Insolation Flux | 14.2074 S⊕ (~19,336 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 324.700 LY (99.556 pc) |