A near-Earth object is not a type of celestial body.
Apollo 8 , the second human spaceflight mission in the United States Apollo space program , was launched on December 21 , 1968 , and became the first crewed spacecraft to leave Earth orbit , reach the Earth 's Moon , orbit it and return safely to Earth . A near-Earth object ( NEO ) is any small Solar System body whose orbit brings it into proximity with Earth .