Kerberos is a small natural satellite of Pluto, about km (mi) in its longest dimension. It was the fourth moon of Pluto to be discovered and its existence was announced on 20 July 2011. It was imaged, along with Pluto and its four other moons, by the New Horizons spacecraft in July 2015. Only two images were obtained. The first image was released to the public on 22 October 2015.