TOI-2015 c
Astrophysical Synthesis & Habitability Characterization
TOI-2015 c 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 2025 by Multiple Observatories using the Transit Timing Variations detection technique (producing an estimated primary transit depth of 0.6736% across the stellar disk), this world measures 2.93 Earth radii and has a measured mass of 8.91 Earth masses. Combining its mass and radius yields a mean bulk density of 1.95 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1.04 g⊕ (10.2 m/s²), and an escape velocity of 19.5 km/s.
In its orbital architecture around TOI-2015, TOI-2015 c completes one full revolution every 5.583 Earth days at a semi-major axis of 0.041232 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 80.3 km/s (compared to Earth's 29.8 km/s). With a near-circular eccentricity of e = 0.00033 (ranging from 0.0412 AU at periapsis to 0.0412 AU at apoapsis), the planet experiences minimal orbital distance variation.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 448 K (+175°C / +347°F) and receiving 6.68 S⊕ (~9,091 W/m²), TOI-2015 c 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 c sharing its stellar neighborhood alongside TOI-2015 b.
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: Multiple Observatories · 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) | 0.041232 AU |
| Orbital Period | 5.583 days |
| Mean Orbital Velocity | 80.3 km/s |
| Orbital Eccentricity (e) | 0.00033 |
| Orbital Inclination (i) | 85.7000° |
| Mean Bulk Density | 1.95 g/cm³ (19.5 km/s vesc) |
| Insolation Flux | 6.6800 S⊕ (~9,091 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 154.400 LY (47.344 pc) |