TOI-1243 b
Astrophysical Synthesis & Habitability Characterization
TOI-1243 b is a confirmed sub-neptune exoplanet orbiting the star TOI-1243, located approximately 140.9 light-years (43.19 parsecs) from the Solar System. First announced in 2026 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.1747% across the stellar disk), this world measures 2.33 Earth radii and has a measured mass of 7.7 Earth masses. Combining its mass and radius yields a mean bulk density of 3.36 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.42 g⊕ (13.93 m/s²), and an escape velocity of 20.3 km/s.
In its orbital architecture around TOI-1243, TOI-1243 b completes one full revolution every 4.659 Earth days.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 450 K (+177°C / +351°F) and receiving 17.27 S⊕ (~23,500 W/m²), TOI-1243 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-1243 is classified as a low-mass red dwarf of spectral type M2.0 V with an effective photospheric temperature of 3,515 K, a radius of 0.511 R☉, a mass of 0.515 M☉, an estimated bolometric luminosity of 0.036 L☉. Stellar evolution modeling indicates a metallicity of [Fe/H] = -0.2 dex (metal-poor relative to the Sun). From Earth, TOI-1243 shines at apparent V-band magnitude 13.427 (faint and requiring research-grade or CCD telescopic photometry) in the Northern 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-1243 |
| Spectral Type | M2.0 V |
| Effective Temp (Teff) | 3,515 K |
| Stellar Radius | 0.5110 R☉ |
| Stellar Mass | 0.5150 M☉ |
| Bolometric Luminosity | 0.036 L☉ |
| Metallicity [Fe/H] | -0.200 dex |
| Stellar Age | — |
| Apparent Magnitude | V: 13.427 · G: 12.359 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | — |
| Orbital Period | 4.659 days |
| Orbital Eccentricity (e) | Circular (0.00) |
| Orbital Inclination (i) | 88.2400° |
| Mean Bulk Density | 3.36 g/cm³ (20.3 km/s vesc) |
| Insolation Flux | 17.2664 S⊕ (~23,500 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 140.900 LY (43.187 pc) |