Kepler’s laws

There has always been a great interest in the motion of planets. By the 16th century, a lot of data on the motion of planets had been collected by many astronomers. Based on these data, Johannes Kepler derived three laws that govern the planets’ motion. These are called Kepler’s laws.

Fig – Kepler’s first law of Planetary motion

Fig – Kepler’s second law of Planetary motion

Fig – Kepler’s third law of Planetary motion

i) The orbit of a planet is an ellipse with the Sun at one of the foci, as shown in the figure given below. In this figure
is the position of the Sun.
ii) The line joining the planet and the Sun sweep equal areas in equal intervals of time.
iii) The cube of the mean distance of a planet from the Sun is proportional to the square of its orbital period T. Or, r3/T2 = constant.

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