Kepler-1304 b

Astrophysical Synthesis & Habitability Characterization

Kepler-1304 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-1304, located approximately 7097.4 light-years (2176.08 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0672% across the stellar disk), this world measures 2.29 Earth radii and has a measured mass of 5.86 Earth masses. Combining its mass and radius yields a mean bulk density of 2.69 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.12 g⊕ (10.98 m/s²), and an escape velocity of 17.9 km/s.

In its orbital architecture around Kepler-1304, Kepler-1304 b completes one full revolution every 16.129 Earth days at a semi-major axis of 0.1202 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 81.1 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 715 K (+442°C / +828°F) and receiving 61.87 S⊕ (~84,205 W/m²), Kepler-1304 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star Kepler-1304 is classified as a stellar host with an effective photospheric temperature of 5,259 K, a radius of 0.81 R☉, a mass of 0.85 M☉, an estimated bolometric luminosity of 0.45 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.68 Gyr and a metallicity of [Fe/H] = -0.05 dex (near-solar heavy-element abundance). From Earth, Kepler-1304 shines at apparent V-band magnitude 15.408 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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