Kepler's Laws of Planetary Motion

Kepler's Laws of Planetary Motion

Johannes Kepler was a German astronomer, mathematician, and astrologer. Johannes Kepler published his first two laws about planetary motion in 1609 and Kepler's third law was published in 1619.

First law of Kepler: 

" The orbit of a satellite is an ellipse from the center of earth at one focus " or " Each planet's orbit about the Sun is an ellipse ".

The Sun's center is always located at one focus of the orbital ellipse.

Kepler's first law of planetary motion

Second law of Kepler: 

" The line joining from the center of earth and satellite sweeps over equal area in equal time interval " or " The imaginary line joining a planet and the Sun sweeps equal areas of space during equal time intervals as the planet orbits ".

If, the area A1 in 6 days and the area A2 in 6 days

So, Area A1 = Area A2

Kepler's second law of planetary motion

Third law of Kepler:

" The squares of the orbital periods of the planets are directly proportional to the cubes of the semi major axes of their orbits " or " The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit ".

Using Newton's Law of gravitation,

Where, " T " is the orbital period of the planet and " r " is the semi-major axis of the orbit.

( YouTube video from NASASolarSystem )

Thank You.