In ancient Egypt there were seven known planets: the Sun, the Moon, Mercury, Venus, Mars, Jupiter and Saturn. Each planet had a special day, and so the 7-day week started. Later the Romans also used this system, which we still have today.
However we now understand that the Sun is not like a planet, it is a star. And we have also decided that the Moon is not a planet because it does not orbit the Sun, it orbits the Earth, and is therefore a satellite.
Nevertheless the Sun has a day named after it: Sunday. The original Roman word was ‘solis’ which became ‘soleil’ in French and ‘sonn’ in German, and the Germanic goddess of the sun was ‘Sunne’, which is how the English word became ‘sun’.
The picture below is an old German ‘sun’ made from metal.