What is the shape of a planet's orbit? Who is crdited with this discovery?

Answer 1

Johannes KEPLER was the one who discovered (through observation) that all orbits are elliptic, with the sun at one of the foci.

This is actually known as the first Kepler's law.
The second law is the law of equal areas: "A line joining a planet and the sun sweeps out equal areas during equal intervals of time."
The third law tells us about orbital periods: "The squares of the orbital periods of planets are directly proportional to the cubes of the semi-major axis of the orbits."

Kepler's laws were later confirmed by Newton's theory on gravitation.

Answer 2

As it is never a perfect circle, it is closest to an ellipse though many planets have wobbles in them due to gravitational pull from other celestial bodies.

Kepler, a brilliant German mathematician, derived three laws, in part, by studying the observations of the legendarily precise Danish astronomer Tycho Brahe.

The first law says: "The orbit of every planet is an ellipse with the sun at one of the foci."

The second law: "A line joining a planet and the sun sweeps out equal areas during equal intervals of time."

The third law : "The squares of the orbital periods of planets are directly proportional to the cubes of the semi-major axis of the orbits."

Answer 3

The orbit changes from nearly circular with an eccentricity of 0.005 to and elliptical orbit with an eccentricity of 0.058. Our current eccentricity is 0.017. The change in orbit is caused by the gravitational pull of the other planets. Changes in the orbit happen about 95, 125, and 400 thousand years. These changes are called the Milankovitch cycles after the man who figured out that equation to explain it.

More information on the Milankovitch cycles can be found at
http://en.wikipedia.org/wiki/Milankovitch_cycles
http://www.homepage.montana.edu/~geol445/hyperglac/time1/milankov.htm
http://geography.about.com/od/learnabouttheearth/a/milankovitch.htm

Answer 4

ORBIT are in shape of an ELLIPSE