He published a book introducing the idea that the sun is the center of the universe in the heliocentric model​, to explain the problems of the geocentric model.

It came from the Greek planetes which means “wanderer”.

These are the two models in history that attempted to explain the motion of celestial bodies.

It is the movement of an object around another object. The path on which the revolving object moves is called the orbit.

He is a German astronomer, spent years trying to figure out the orbit of Mars. He deduced that the orbit is not circular, but elliptical or an oval.

The line connecting the two points farthest from each other is called __________.

During night time, the multitudes of stars at night seem to form patterns. These patterns are called __________.

Earth’s axis of rotation is tilted at _________ with respect to the plane connecting Earth’s center and the sun’s center

How fast a planet rotates around its axis is called its __________.