What's Up with 'Niku'? Object's Weird Orbit Puzzles Scientists

A mysterious object in the outer reaches of the solar system is revolving around the sun in an abnormal way, and scientists currently cannot explain why. The object has been nicknamed Niku, a Chinese adjective that means "rebellious," by the group of researchers who announced its discovery in August. This name was chosen because the object's orbit is retrograde, meaning it moves in the opposite direction of nearly everything else in the solar system.