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== == An ellipse. Like planets.
The ancient Greeks used Ptolemy's theory, based on circles, that was good enough for the accuracy needed at the time. Later Kepler in the 16th century discovered that an ellipse is a better model of a planetary orbit. In modern times it has been discovered that an ellipse is an approximation and that true orbits have no simple description. But the ellipse is a good enough model for many purposes.
The shape is an "ellipse".
kepler
Johannes Kepler was the first to state that planets move in elliptical orbits.
Johannes Kepler determined that all planets have elliptical orbits.
Johannes Kepler stated that the planets revolve around the sun in an ellipse.
Ellipse
Johannes Kepler
The planetary orbits of our solar system are considered "elliptical." This includes "circular" orbits, as a circle is a type of ellipse. In astrodynamics, an elliptical orbit and a circular orbit both fit into the description of a Kepler Orbit.
Planets orbit the sun in the shape of an ellipse, which is an elongated circle similar to an oval. When it was first discovered that the Sun is the center of the solar system, it was thought that all the planets had a circular orbit, but the calculations didn't fit.
An ellipse.
Ellipse.
Planets orbit in an ellipse.
== == An ellipse. Like planets.
An ellipse.
The ancient Greeks used Ptolemy's theory, based on circles, that was good enough for the accuracy needed at the time. Later Kepler in the 16th century discovered that an ellipse is a better model of a planetary orbit. In modern times it has been discovered that an ellipse is an approximation and that true orbits have no simple description. But the ellipse is a good enough model for many purposes.