An astronomical object, celestial object, stellar object or heavenly object is a naturally occurring physical entity, association, or structure that exists within the universe. In astronomy, the terms object and body are often used interchangeably. However, an astronomical body, celestial body, or heavenly body is a single, tightly bound, contiguous physical object, while an astronomical or celestial object admits a more complex, less cohesively bound structure, which may consist of multiple bodies or even other objects with substructures.