Kepler-540 b

Astrophysical Synthesis & Habitability Characterization

Kepler-540 b is a confirmed sub-neptune exoplanet orbiting the star Kepler-540, located approximately 1273.2 light-years (390.37 parsecs) from the Solar System. First announced in 2016 by Kepler using the Transit detection technique (producing an estimated primary transit depth of 0.0529% across the stellar disk), this world measures 2.71 Earth radii and has a measured mass of 7.8 Earth masses. Combining its mass and radius yields a mean bulk density of 2.16 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 1.06 g⊕ (10.4 m/s²), and an escape velocity of 19 km/s.

In its orbital architecture around Kepler-540, Kepler-540 b completes one full revolution every 172.705 Earth days at a semi-major axis of 0.58822 AU (situated at an orbital separation between Mercury's 0.39 AU and Venus's 0.72 AU). Its mean orbital velocity is approximately 37.1 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 355 K (+82°C / +180°F) and receiving 4.53 S⊕ (~6,159 W/m²), Kepler-540 b orbits interior to the runaway greenhouse boundary where surface liquid water cannot persist.

The host star Kepler-540 is classified as a stellar host with an effective photospheric temperature of 5,946 K, a radius of 1.08 R☉, a mass of 1.02 M☉, an estimated bolometric luminosity of 1.308 L☉. Stellar evolution modeling indicates an estimated stellar age of 4.9 Gyr and a metallicity of [Fe/H] = -0.1 dex (near-solar heavy-element abundance). From Earth, Kepler-540 shines at apparent V-band magnitude 12.293 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere.

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