Who discovered all the planets?

Answer

You can see the planets Mercury, Venus, (Earth), Mars, Jupiter and Saturn with the naked eye from Earth. Look high southwest this evening. The brightest object you see is the planet Jupiter. Around midnight, Mars rises very low in the southeast. In the morning, Venus is visible low in the east. That will change again in a few months.

Our distant ancestors could also see those planets with the naked eye. The ancient Greeks saw that the planets move slowly opposite the stars and called them wandering stars. It is therefore impossible to say who saw them for the first time, for example you cannot say which person saw the sun or the moon for the first time.

Uranus and Neptune, that’s something else. A small stargazer is sufficient for this, but it is not possible without it.

Uranus was discovered by Friedrich Herschel, a German who moved to England at the age of 19 and became a successful astronomer. He discovered a new planet on March 13, 1781, and wanted to name it in honor of the then British King George: “Georgium sidus”. The French and Germans didn’t like that, and at first simply called the planet “Herschel” and “Uranus”. Eventually the British also started using that name and it became Uranus permanently

When astronomers calculated the orbits of the 7 known planets, they found small deviations. Adams in England and Le Verrier in France calculated mathematically where an eighth planet would have to be to cause exactly those anomalies. The planet was indeed found in 1846, very close to the position calculated by Le Verrier. Here, too, there was originally some quarrel about the name. After all, Adams was an Englishman, Le Verrie a Frenchman, but it was the German Galle who first actually saw the planet as a planet.

You can find more details about the discoveries of Uranus and Neptune on wikipedia (especially in the English language one).