Let's take a look at the solar system in this KS3 Science quiz. When you look up at the sky on a clear night, you can see thousands of stars. Humans have been around for many thousands of years but it is only in the last few hundred years that we have started to understand about the universe in which we live.
Ancient civilisations noticed that there were five brighter 'stars' that moved around the sky in a strange way but had no idea about why they behaved like that. We now know these are the planets Mercury, Venus, Mars, Jupiter and Saturn. They are much closer to us than the stars and, like the Earth, they orbit our Sun. They are visible only because they reflect the Sun's light.
When Galileo first pointed the newly-invented telescope at the sky, he noticed that one of these had moons orbiting it (Jupiter).
This backed up the theory that the Earth wasn't actually the centre of the universe and that the Earth could be orbiting the Sun. Saying such a thing in the 1600s was heresy but, luckily for Galileo, he was too important a figure to be murdered by the Catholic Church so they placed him under house arrest instead. He also noticed 'handles' on the planet Saturn - we now realise that these are rings made from rocks, icy blocks and dust. The spacecraft Cassini was sent to study Saturn and was named after the seventeenth century Italian astronomer, Giovanni Cassini, who discovered the four main moons of Saturn and a gap in the rings.