Kepler-1258 b
Astrophysical Synthesis & Habitability Characterization
Kepler-1258 b is a confirmed terrestrial exoplanet orbiting the star Kepler-1258, located approximately 2340.3 light-years (717.56 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0063% across the stellar disk), this world measures 0.86 Earth radii and has a measured mass of 0.566 Earth masses. Combining its mass and radius yields a mean bulk density of 4.91 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 0.77 g⊕ (7.55 m/s²), and an escape velocity of 9.1 km/s.
In its orbital architecture around Kepler-1258, Kepler-1258 b completes one full revolution every 0.985 Earth days at a semi-major axis of 0.01824 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 201.5 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 2335 K (+2062°C / +3744°F) and receiving 2,775.00 S⊕ (~3,776,775 W/m²), Kepler-1258 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.
The host star Kepler-1258 is classified as a stellar host with an effective photospheric temperature of 5,839 K, a radius of 0.99 R☉, a mass of 0.99 M☉, an estimated bolometric luminosity of 1.022 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.89 Gyr and a metallicity of [Fe/H] = -0.07 dex (near-solar heavy-element abundance). From Earth, Kepler-1258 shines at apparent V-band magnitude 13.929 (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-1258 |
| Spectral Type | Unclassified |
| Effective Temp (Teff) | 5,839 K |
| Stellar Radius | 0.9900 R☉ |
| Stellar Mass | 0.9900 M☉ |
| Bolometric Luminosity | 1.022 L☉ |
| Metallicity [Fe/H] | -0.070 dex |
| Stellar Age | 3.890 Gyr |
| Apparent Magnitude | V: 13.929 · G: 13.785 |
| System Architecture | 1 Star, 1 Planet |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.018240 AU |
| Orbital Period | 0.985 days |
| Mean Orbital Velocity | 201.5 km/s |
| Orbital Eccentricity (e) | 0.00000 |
| Orbital Inclination (i) | 89.3300° |
| Mean Bulk Density | 4.91 g/cm³ (9.1 km/s vesc) |
| Insolation Flux | 2775.0000 S⊕ (~3,776,775 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 2340.300 LY (717.555 pc) |