Kepler-1209 b

Astrophysical Synthesis & Habitability Characterization

Kepler-1209 b is a confirmed super-earth exoplanet orbiting the star Kepler-1209, located approximately 1648.8 light-years (505.53 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0101% across the stellar disk), this world measures 1.51 Earth radii and has a measured mass of 2.89 Earth masses. Combining its mass and radius yields a mean bulk density of 4.63 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 1.27 g⊕ (12.45 m/s²), and an escape velocity of 15.5 km/s.

In its orbital architecture around Kepler-1209, Kepler-1209 b completes one full revolution every 25.369 Earth days at a semi-major axis of 0.17515 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 75.1 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 755 K (+482°C / +900°F) and receiving 63.25 S⊕ (~86,078 W/m²), Kepler-1209 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star Kepler-1209 is classified as a stellar host with an effective photospheric temperature of 6,210 K, a radius of 1.38 R☉, a mass of 1.23 M☉, an estimated bolometric luminosity of 2.541 L☉. Stellar evolution modeling indicates an estimated stellar age of 3.09 Gyr and a metallicity of [Fe/H] = 0.12 dex (metal-rich relative to the Sun). From Earth, Kepler-1209 shines at apparent V-band magnitude 12.554 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

Discovery Facility: Kepler · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).