Google it and I bet you find the correct answer
a fixed luminous point in the night sky which is a large, remote incandescent body like the sun. or a conventional or stylized representation of a star, typically one having five or more points.
Well the object will have no Momentum since it is not moving, so a small object that is going 10 mph will have Momentum.
Explanation:
in my opinion I'd say it's gravity because it's making the book stay in it's one and only position pulling the book at the center of the desk