What Are Orbits?

Cause

• An orbit is the delicate balance between an object moving in a straight line through space and the force of gravity acting on the object. If the forward momentum is greater than the force of gravity, the object will move away and not orbit. If the force of gravity is greater than the momentum, the objects will collide. Only the perfect combination of the force of gravity and the momentum will cause an orbit to occur.

Shape

• The shape of an orbit is an ellipse.The more massive object is located at one focus of the ellipse while the satellite follows the ellipse.The further the foci are from each other, the more elliptical the orbit.

Distance and Mass

• Objects with greater mass exert greater gravity. Therefore, more satellites can orbit, and these orbits can exist at a further distance from the object. The gravitational effect decreases with distance. Therefore, the greater the distance, the less chance passing objects have of forming an orbit.

Time

• A satellite will sweep out equal areas of the ellipse in equal amounts of time. In other words, a satellite will move faster in its orbit when it is closest to the object it revolves around and move slower when it is farthest from the object it revolves around.

Escape Velocity

• Escape velocity is the velocity an object must go to break free from the planet. To send man-made satellites into orbit, they must be launched faster than seven miles per second. The orbital velocity to maintain orbit at 150 miles above the Earth's surface is 17,000 mph.

Barycenter

• The barycenter is the center of mass between two objects. When one object orbits another, they are actually both orbiting the barycenter. Most of the time, the barycenter is located within the more massive object, but not centered. Therefore, the more massive object may wobble in its own orbit as the satellite revolves.