The sun and its family of planets which is our immediate neighborhood is known as the solar system. The planets' moons or their natural satellites, comets, asteroids and meteoroids are all included in the solar system. Everything inside the solar system is held together with the help of the sun's gravity.
There are 8 planets in the solar system. Actually there were 9 but Pluto is not now included as a planet because of several reasons. (I will mention them later in another post).
The Inner Planets
Mercury, Venus, Earth and Mars are considered as inner planets because they lie on the inner side of the asteroid belt which orbit the sun. The planets formed about 4.6 billion years ago and all these inner planets were formed from dust particles and they ended up being rocky planets.
Outer Planets
Jupiter, Saturn, Uranus and Neptune are considered as outer planets as they are located outside the asteroid belt. They are also known as gas giants.
Models of the Solar System
Above is a picture of the heliocentric model which was explained by Sir Nicholas Copernicus. Later Johannes Kepler improved this model.
Early astronomers believed that the sun and all the other planets revolved around the Earth. This concept is known as the geocentric model of the solar system. The heliocentric model which placed the sun at the centre was first introduced by Aristarchus of Samos and was later explained and developed by Sir Nicholas Copernicus. Galileo Galilee's observations with his newly made telescope strongly supported the heliocentric model.
