Elliptical Orbit

For the longest time astronomers thought the Universe existed as a perfect sphere; each planet and star following a perfect spherical path. During the early times of the church, the accepted belief was the Earth was the center of the Universe. This would later be disproved by astronomers.

Johan Kepler discovered the elliptical orbit. Kepler was the first person to theorize that the planets actually move in ovaloid orbits. The equation he used to prove this would later become known as the Planetary Laws of Motion and was further supported by Sir Issac Newton’s Theory of Gravity. According to Newton, gravity is the reason planets and stars and other celestial objects orbit around each other. The bigger the celestial body, the more mass it can exert on smaller objects around it. One massive body, acting alone would create a circular orbit. If there’s more than one massive celestial body, the orbiting object will have have an eccentric or elliptical orbit.

This has many consequences, not on how we observe space but also how navigate it. Other than the threat of running into random objects, gravity is one of the greatest concerns for spaceflight. Normally a planet or some other celestial object has enough mass and speed to avoid being completely pulled into a star’s center. But in the case of man made space the difference of size is so great that this danger can’t be discounted. To cope with this threat from gravitational fields Aeronautics has come up with two solutions. One is speed. Thanks to advances in rocketry we now have craft that can match the orbit speeds of larger more massive objects in space this helps to reduce the pull of gravity on the craft. We can actually harvest gravity’s power. This is known as a gravity assist or gravity slingshot. Due to the elliptical nature of most orbits, There is are two extreme points in the orbit called the apsis. One point is closest to one of foci and the other is farthest away from that same focus. This causes a change in the speed of an object’s orbit. The closer it gets the faster it moves the farther it gets the slower it moves. A spacecraft can take advantage of this to boost its speed and escape orbit which also has the added benefit of saving fuel.

If you enjoyed this article there are several others on Universe Today you might enjoy. There is an article on geostationary orbit that you will find very informative. Another article is about the Earth’s orbit.

There also other great articles and resources on the web that you can check out. Such as this University of Michigan website. It also has some interesting animation that illustrate elliptical orbits. The University of Indiana website has an interesting orbit calculator you should also check out.

Astronomy cast also has an episode that is pertinent to this article. Be sure to check out the Question Episode on Planetary Orbits

Sources: NASA Earth Observatory

Tagged as: eccentric, elliptical, gravity, Kepler, orbit, Satellites