All of the planets of our solar system rotate around the sun on an elliptical orbit. An elliptical orbit occurs in the shape of an ellipsis. An ellipsis is similar to an oval, a circular shape with two sides flatter than the others. A 17th century mathematician and astronomer, Johannes Kepler, was first to identify the three components of an elliptical orbit. The shape of the elliptical orbit for each of the planets in our solar system varies based on the variables of these components.
Focus
An elliptical orbit has two foci, which means two focus points. This may seem confusing because we know that our planet orbits around only one object, the sun. Kepler defined the focus as the points at which the sum of the distances to the foci from any one point in the elliptical orbit remains a constant. The second foci would not be a relevant point if the earth were in a circular orbit. In a circular orbit, the distance from the earth to the sun would be a constant. In an elliptical orbit, the distance from the earth to the sun is constantly changing.
Axes
An elliptical orbit has two axes, the major axis and the minor axis. The major axis is the length of the axis from crest to crest. The minor axis is the length of the ellipses from the middle of one of it's flat sides to it's other flat side. The major axis is always longer than the minor axis. Half of the major axis equals the semimajor axis of the ellipses. The radius of an ellipses is the same as the length of it's semimajor axis.
Eccentricity
The eccentricity of an elliptical orbit refers to the severity at which the shape of the orbit strays from a perfect circle. An orbit where two sides of the ellipses are only slightly flat is an orbit with little eccentricity. An orbit with a high level of eccentricity would look like a circle that has been squished until it is long and flat. The earth rotates around the sun with very low eccentricity, or a very circular orbit. Planets further away from the sun have higher levels of eccentricity. The further away a planet is from the sun, the flatter it's elliptical orbit is.
Perihelion and Aphelion
The perihelion is the point in an elliptical orbit when the planet is closest to the sun. The gravitational force of the sun causes the planet to travel at it's fastest when it is at the perihelion. The aphelion is the point in an elliptical orbit when the planet is furthest away from the sun. When the planet is at it's aphelion, it travels the slowest.
Member Comments