TOI-2015 b
Astrophysical Synthesis & Habitability Characterization
TOI-2015 b is a confirmed sub-neptune exoplanet orbiting the star TOI-2015, located approximately 154.4 light-years (47.34 parsecs) from the Solar System. First announced in 2023 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.8591% across the stellar disk), this world measures 3.309 Earth radii (0.3 Jupiter radii) and has a measured mass of 9.2 Earth masses. Combining its mass and radius yields a mean bulk density of 1.4 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 0.84 g⊕ (8.24 m/s²), and an escape velocity of 18.7 km/s.
In its orbital architecture around TOI-2015, TOI-2015 b completes one full revolution every 3.348 Earth days at a semi-major axis of 0.029322 AU (an ultra-close orbit less than one-seventh of Mercury's 0.387 AU distance from the Sun, where strong stellar tidal forces typically induce synchronous rotation). Its mean orbital velocity is approximately 95.3 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.0789 carries the world between 0.027 AU at periapsis and 0.0316 AU at apoapsis, driving measurable seasonal insolation cycles.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 531 K (+258°C / +496°F) and receiving 13.19 S⊕ (~17,945 W/m²), TOI-2015 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-2015 is classified as a low-mass red dwarf of spectral type M4 +/- 0.5 with an effective photospheric temperature of 3,297 K, a radius of 0.3273 R☉, a mass of 0.3041 M☉, an estimated bolometric luminosity of 0.011 L☉. Stellar evolution modeling indicates an estimated stellar age of 5.5 Gyr and a metallicity of [Fe/H] = -0.31 dex (metal-poor relative to the Sun). From Earth, TOI-2015 shines at apparent V-band magnitude 16.11 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The TOI-2015 system is a multi-planet architecture hosting 2 confirmed worlds, with TOI-2015 b sharing its stellar neighborhood alongside TOI-2015 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-2015 |
| Spectral Type | M4 +/- 0.5 |
| Effective Temp (Teff) | 3,297 K |
| Stellar Radius | 0.3273 R☉ |
| Stellar Mass | 0.3041 M☉ |
| Bolometric Luminosity | 0.011 L☉ |
| Metallicity [Fe/H] | -0.310 dex |
| Stellar Age | 5.500 Gyr |
| Apparent Magnitude | V: 16.110 · G: 14.176 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.029322 AU |
| Orbital Period | 3.348 days |
| Mean Orbital Velocity | 95.3 km/s |
| Orbital Eccentricity (e) | 0.07890 |
| Orbital Inclination (i) | 87.6100° |
| Mean Bulk Density | 1.4 g/cm³ (18.7 km/s vesc) |
| Insolation Flux | 13.1850 S⊕ (~17,945 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 154.400 LY (47.344 pc) |