Kepler-1869 c
Astrophysical Synthesis & Habitability Characterization
Kepler-1869 c is a confirmed sub-earth exoplanet orbiting the star Kepler-1869, located approximately 368.6 light-years (113.03 parsecs) from the Solar System. First announced in 2023 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0057% across the stellar disk), this world measures 0.74 Earth radii and has a measured mass of 0.33 Earth masses. Combining its mass and radius yields a mean bulk density of 4.49 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 0.6 g⊕ (5.88 m/s²), and an escape velocity of 7.5 km/s.
In its orbital architecture around Kepler-1869, Kepler-1869 c completes one full revolution every 1.717 Earth days at a semi-major axis of 0.028 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 177.4 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 1455 K (+1182°C / +2160°F) and receiving 1,056.84 S⊕ (~1,438,359 W/m²), Kepler-1869 c orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-1869 is classified as a stellar host with an effective photospheric temperature of 5,808 K, a radius of 0.902 R☉, a mass of 0.987 M☉, an estimated bolometric luminosity of 0.831 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.29 Gyr and a metallicity of [Fe/H] = -0.06 dex (near-solar heavy-element abundance). From Earth, Kepler-1869 shines at apparent V-band magnitude 10.31 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Kepler-1869 system is a multi-planet architecture hosting 2 confirmed worlds, with Kepler-1869 c sharing its stellar neighborhood alongside Kepler-1869 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: Kepler · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | Kepler-1869 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,808 K |
| Stellar Radius | 0.9020 R☉ |
| Stellar Mass | 0.9870 M☉ |
| Bolometric Luminosity | 0.831 L☉ |
| Metallicity [Fe/H] | -0.060 dex |
| Stellar Age | 1.290 Gyr |
| Apparent Magnitude | V: 10.310 · G: 10.091 |
| System Architecture | 1 Star, 2 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.028000 AU |
| Orbital Period | 1.717 days |
| Mean Orbital Velocity | 177.4 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 81.3800° |
| Mean Bulk Density | 4.49 g/cm³ (7.5 km/s vesc) |
| Insolation Flux | 1056.8400 S⊕ (~1,438,359 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 368.600 LY (113.025 pc) |