It was months and years of difficult geometrical calculations from measurements made by Tycho Brahe, by his employee Johannes Kepler.
When Tycho was alive he would not let Kepler see the results of his work, but he let slip a few figures, tantalisingly, now and again. But after Tycho's death Kepler was clever and devious enough to get his hands on the results, which was fortunate because he had the ability to make use of them.
Kepler chose the orbit of Mars as a special subject, which was lucky because it has a relatively high eccentricity that shows up the difference between an ellipse and a circular orbit. After some false starts he realised that the figures fitted an elliptical orbit. Subsequently further observations demonstrated that elliptical orbits gave correct predictions of the positions of Mars and the other planets.
Kepler used the heliocentric principle, with the Sun at the centre. Although Kepler and Galileo were contemporary, Galileo never believed that the planets' orbits could be elliptical, and he stuck to the old systems of circles and epicycles of Ptolemy and Copernicus.
Johannes Kepler was the first to state that planets move in elliptical orbits.
All planets actually follow an elliptical orbit.
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.
Johannes Kepler formulated the laws of planetary motion in the early 17th century, including the discovery that planets move in elliptical orbits with the sun at one of the foci.
The discovery that planets travel in elliptical orbits was made by Johannes Kepler. In the early 17th century, Kepler formulated his First Law of Planetary Motion, which states that planets move around the Sun in elliptical paths, with the Sun at one focus of the ellipse. This groundbreaking work built upon the precise observational data collected by Tycho Brahe. Kepler's laws significantly advanced the understanding of planetary motion and the heliocentric model of the solar system.
Kepler
Johannes Kepler was the first to state that planets move in elliptical orbits.
Planetary orbits are usually in the shape of an ellipse.
All planets actually follow an elliptical orbit.
Johannes Kepler.
The person who first stated this was Johannes Kepler.
It is Kepler's first law which says the planet moves in an ellipse with the Sun occupying one focus and the other focus is vacant.
Copernicus
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.
Johannes Kepler formulated the laws of planetary motion in the early 17th century, including the discovery that planets move in elliptical orbits with the sun at one of the foci.
The discovery that planets travel in elliptical orbits was made by Johannes Kepler. In the early 17th century, Kepler formulated his First Law of Planetary Motion, which states that planets move around the Sun in elliptical paths, with the Sun at one focus of the ellipse. This groundbreaking work built upon the precise observational data collected by Tycho Brahe. Kepler's laws significantly advanced the understanding of planetary motion and the heliocentric model of the solar system.
No, the orbits of planets are not perfectly circular but are elliptical in shape. The path of planets around the Sun can be best described using Kepler's laws of planetary motion, which state that planets move in elliptical paths with the Sun at one of the foci of the ellipse.