What were the discoveries of astronomers like Copernicus and Galileo?

Their discoveries both had to do with the relationship of the earth to the sun and universe. That the earth wasn't the centre of the universe and that the sun didn't rotate round the earth but rather the other way.

Explanation:

Nicolaus Corpenicius (19 February 1473 - 24 May 1543) was a scientist, astronomer and renaissance era polymath, who was fascinated with stars. He was the first to formulate a model of the universe that had the sun at the centre of the universe instead of the earth. It was such a groundbreaking discovery. Corpenicus is often referred to as the father of Modern Astronomy.

Galileo Galilie (15 February 1564 - 8 January 1642) was an italian physics philosopher who was famous for his discovery that the earth rotated round the sun. it was a big deal in his time, because, the prevailing thought in his day, was that the earth was the centre of the universe and the sun rotated round the verse. Though Corpenicus was the first to discover and publish it. Further discoveries and inventions by Galileo proved corpenicus as true.