TOI-1836 c
Astrophysical Synthesis & Habitability Characterization
TOI-1836 c is a confirmed sub-neptune exoplanet orbiting the star TOI-1836, located approximately 625.1 light-years (191.65 parsecs) from the Solar System. First announced in 2024 by Transiting Exoplanet Survey Satellite (TESS) using the Transit detection technique (producing an estimated primary transit depth of 0.021% across the stellar disk), this world measures 2.6 Earth radii and has a measured mass of 8 Earth masses. Combining its mass and radius yields a mean bulk density of 2.51 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.18 g⊕ (11.57 m/s²), and an escape velocity of 19.6 km/s.
In its orbital architecture around TOI-1836, TOI-1836 c completes one full revolution every 1.773 Earth days at a semi-major axis of 0.03089 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 189.6 km/s (compared to Earth's 29.8 km/s). The orbit is modeled as circular (e = 0.00), maintaining a constant stellar distance throughout its year.
⚠️ Thermal Regime (Irradiated / Hot Zone): At an equilibrium temperature of 2008 K (+1735°C / +3155°F) and receiving 3,983.42 S⊕ (~5,421,430 W/m²), TOI-1836 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star TOI-1836 is classified as a stellar host with an effective photospheric temperature of 6,237 K, a radius of 1.6454 R☉, a mass of 1.2518 M☉, an estimated bolometric luminosity of 3.676 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.2 Gyr and a metallicity of [Fe/H] = -0.136 dex (metal-poor relative to the Sun). From Earth, TOI-1836 shines at apparent V-band magnitude 9.765 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The TOI-1836 system is a multi-planet architecture hosting 2 confirmed worlds, with TOI-1836 c sharing its stellar neighborhood alongside TOI-1836 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: Transiting Exoplanet Survey Satellite (TESS) · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | TOI-1836 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 6,237 K |
| Stellar Radius | 1.6454 R☉ |
| Stellar Mass | 1.2518 M☉ |
| Bolometric Luminosity | 3.676 L☉ |
| Metallicity [Fe/H] | -0.136 dex |
| Stellar Age | 3.200 Gyr |
| Apparent Magnitude | V: 9.765 · G: 9.645 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.030890 AU |
| Orbital Period | 1.773 days |
| Mean Orbital Velocity | 189.6 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 2.51 g/cm³ (19.6 km/s vesc) |
| Insolation Flux | 3983.4169 S⊕ (~5,421,430 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 625.100 LY (191.649 pc) |