Kepler 78b is an exoplanet nicknamed the Hell Planet, orbiting the star Kepler 78 in Cygnus. The planet is 69 per cent more massive than Earth and 20% larger in terms of diameter. It gets its nickname from its extreme temperature, which has been estimated at between 2300 and 3100 Kelvin. This in turn is due to the planet??? extreme proximity to its star ??it orbits 40 times closer in than Mercury in our Solar System, completing an orbit in a mere 8.5 hours. This illustration imagines the Hell Planet from the surface of an orbiting moon.