An astronomical object or celestial object is a naturally occurring physical entity, association, or structure that exists in the observable universe .  In
astronomy , the terms "object" and "body" are often used interchangeably. However, an astronomical body or
celestial body is a single, tightly bound contiguous entity, while an astronomical or celestial object is a complex, less cohesively bound structure, that may consist of multiple bodies or even other objects with substructures.
Examples for astronomical objects include planetary systems , star clusters ,
nebulae and galaxies, while asteroids,
moons , planets, and stars are astronomical bodies. A comet may be identified as both body and object: It is a body when referring to the frozen
nucleus of ice and dust, and an object when describing the entire comet with its diffuse coma and tail .