The most distant object ever explored by spacecraft is a reddish, snowman-shape rock 4 billion miles from Earth.The object, nicknamed Ultima Thule, was photographed by NASA’s New Horizons spacecraft during a late-night rendezvous on the first day of 2019. It is the first inhabitant of the Kuiper belt - the ring of rocky relics that surrounds the outer solar system - that scientists have seen up close.Its odd shape, which scientists term a “contact binary,” indicates that it formed as two spherical rocks slowly fused together in the early days of the solar system.