Kepler-1870 b
Astrophysical Synthesis & Habitability Characterization
Kepler-1870 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-1870, located approximately 1328.2 light-years (407.22 parsecs) from the Solar System. First announced in 2021 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0526% across the stellar disk), this world measures 2.101 Earth radii and has a measured mass of 5.07 Earth masses. Combining its mass and radius yields a mean bulk density of 3.01 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.15 g⊕ (11.28 m/s²), and an escape velocity of 17.4 km/s.
In its orbital architecture around Kepler-1870, Kepler-1870 b completes one full revolution every 3.607 Earth days at a semi-major axis of 0.0452 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 136.3 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 1046 K (+773°C / +1423°F) and receiving 287.60 S⊕ (~391,424 W/m²), Kepler-1870 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-1870 is classified as a stellar host with an effective photospheric temperature of 5,508 K, a radius of 0.84 R☉, a mass of 0.955 M☉, an estimated bolometric luminosity of 0.583 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.79 Gyr and a metallicity of [Fe/H] = 0.07 dex (metal-rich relative to the Sun). From Earth, Kepler-1870 shines at apparent V-band magnitude 13.566 (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: Kepler · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | Kepler-1870 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,508 K |
| Stellar Radius | 0.8400 R☉ |
| Stellar Mass | 0.9550 M☉ |
| Bolometric Luminosity | 0.583 L☉ |
| Metallicity [Fe/H] | 0.070 dex |
| Stellar Age | 0.790 Gyr |
| Apparent Magnitude | V: 13.566 · G: 13.420 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.045200 AU |
| Orbital Period | 3.607 days |
| Mean Orbital Velocity | 136.3 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 86.6800° |
| Mean Bulk Density | 3.01 g/cm³ (17.4 km/s vesc) |
| Insolation Flux | 287.6000 S⊕ (~391,424 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1328.200 LY (407.216 pc) |