# keplers’ laws of planetary motion.pdf - KEPLERS’ LAWS OF...

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KEPLERS’ LAWS OF PLANETARY MOTION
1STLAWThe orbit of every planet is an ellipse withthe Sun at a focus.
2NDLAWA line joining a planet & the Sun sweepsout equal areas during equal intervals oftime.
3RDLAWThe square of the orbital period of a planetis directly proportional to the third power ofthe semi-major axis (a) of its orbit.Moreover, the constant of proportionalityhas the same value for all planets.
IN OTHER WORDS:Kepler's third law of planetary motion is a mathematical relationbetweenorbital periods and distances.It allows astronomers to measure masses of celestial objects.Kepler's third law, which is often called the harmoniclaw,is a mathematical relationship between the time ittakes the planet to orbit the Sun and the distancebetween the planet and the Sun.
The time it takes for a planet to orbit the Sun is itsorbital period, which is often simply called its period.For the average distance between the planet andthe Sun, Kepler used what we call the semi-majoraxis of the ellipse.

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Mass, Planet, Kepler s laws of planetary motion, Celestial mechanics