The Solar System

The solar system contains the Sun, planets and other objects such as comets.

The Sun, which forms part of our solar system, is the closest star to the Earth. It takes just over eight minutes for light from the Sun to reach Earth.

The 8 planets in the solar system are:

1. Mercury

2. Venus

3. Earth

4. Mars

5. Jupiter

6. Saturn

7. Uranus

8. Neptune

This is the order of the planets, starting with the one closest to the Sun. So, Mercury is closest to the Sun.

An easy way to remember the order is:

  • My Very Easy Method Just Speeds Up Naming

Scientists have been debating Pluto’s classification as a planet. Since its discovery in 1930, Pluto has been considered the ninth planet. But in 2006, it was downgraded to a dwarf planet.

Heliocentric Model

The diagram below shows the heliocentric model of our solar system, With the Sun at the centre and the planets orbiting it.

It takes around 365 days for the Earth to orbit the Sun. However, the duration of orbits are different for different planets.

Inner and outer planets

The inner planets are made of rock and the outer planets are gas giants.

Geocentric model

People did not always believe that the Sun was the centre of the solar system. Initially, the geocentric model was more popular.

In the geocentric model, the Earth is at the centre, with the Sun, Moon, stars and planets orbiting the Earth. The geocentric model is the older, outdated model.

While standing on Earth and seeing the Sun move across the sky, people believed that the Earth was at the centre and that the correct model was the geocentric model. However, we now know that the Earth is at the centre and the planets orbit the Sun.