Kepler-1678 b

Astrophysical Synthesis & Habitability Characterization

Kepler-1678 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-1678, located approximately 2763.6 light-years (847.34 parsecs) from the Solar System. First announced in 2020 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.1316% across the stellar disk), this world measures 3.304 Earth radii (0.29 Jupiter radii) and has a measured mass of 10.9 Earth masses. Combining its mass and radius yields a mean bulk density of 1.67 g/cm³ (a low bulk density dominated by an extended hydrogen-helium gaseous envelope), a surface gravity of 1 g⊕ (9.81 m/s²), and an escape velocity of 20.3 km/s.

In its orbital architecture around Kepler-1678, Kepler-1678 b completes one full revolution every 147.974 Earth days at a semi-major axis of 0.5302 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 39 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.

☁️ Atmospheric Regime (Volatile / Gas Envelope): With a radius of 3.304 R⊕, Kepler-1678 b exceeds the empirical ~1.8–2.2 R⊕ Fulton radius valley threshold, indicating a substantial hydrogen-helium or supercritical volatile envelope without a conventional solid terrestrial surface.

The host star Kepler-1678 is classified as a stellar host with an effective photospheric temperature of 5,754 K, a radius of 0.835 R☉, a mass of 1.03 M☉, an estimated bolometric luminosity of 0.686 L☉. Stellar evolution modeling indicates an estimated stellar age of 0.3 Gyr and a metallicity of [Fe/H] = 0 dex (near-solar heavy-element abundance). From Earth, Kepler-1678 shines at apparent V-band magnitude 15.02 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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