Kepler-556 b

Astrophysical Synthesis & Habitability Characterization

Kepler-556 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-556, located approximately 2200.2 light-years (674.6 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0439% across the stellar disk), this world measures 2.24 Earth radii and has a measured mass of 5.65 Earth masses. Combining its mass and radius yields a mean bulk density of 2.77 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.13 g⊕ (11.08 m/s²), and an escape velocity of 17.8 km/s.

In its orbital architecture around Kepler-556, Kepler-556 b completes one full revolution every 11.723 Earth days at a semi-major axis of 0.09833 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 91.3 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 766 K (+493°C / +919°F) and receiving 81.64 S⊕ (~111,113 W/m²), Kepler-556 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star Kepler-556 is classified as a stellar host with an effective photospheric temperature of 5,740 K, a radius of 0.98 R☉, a mass of 1 M☉, an estimated bolometric luminosity of 0.935 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.17 Gyr and a metallicity of [Fe/H] = 0.03 dex (near-solar heavy-element abundance). From Earth, Kepler-556 shines at apparent V-band magnitude 14.316 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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