The Sun serves as the center of the solar system with other planets surrounding it and they all travel in an orbit. They are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto.
The four smaller planets i.e. Mercury, Venus, Earth and Mars are called terrestrial planets which are made of rock and metals, while the other ones are called gas giants and are more massive. The solar system also contain the meteoroids, comets and asteroids
The Kepler’s laws describe the planetary motion of objects around the sun and they are:
- The planet each travel along an ellipse with the sun as the focus
- The line joining the sun and other planets sweep out equal area at equal time
- The square of the period of revolutions of the planet are proportional to the cubes of their mean distances from the sun
(T2 ∝ r3)
Kepler’s law shows that the speed of revolution of a planet round the sun is not uniform, but changes as the planet moves round the sun.