In fact objects on Earth slow down due to friction, an object at rest would stay at rest even if in vacuum, and celestial bodies, as anything else, move in a straight line at constant speed or remain at rest unless acted by forces.
(celestial bodies; move; in a straight line at constant speed) (celestial bodies; remain; at rest) (an object at rest; would stay; at rest) Context(an object at rest would stay,List([52, 80))):(In fact objects on Earth; slow down; due to friction)
an object at rest would stay,List([52, 80))
celestial bodies celestial bodies an object at rest In fact objects on Earth
move remain would stay slow down
in a straight line at constant speed
at rest
at rest
due to friction