Nicolaus Copernicus developed the idea that all the planets orbit around the sun and not around the earth.
Edmond Halley discovered the repetition of the comets and how they return over an over again in the same amount of time.
Galileo used a refracting telescope to discover three of Jupiters four largest moons.
Johannes Kepler invented the three Laws of Planetary Motion.
G.D. Cassini discovered the division in the rings of Saturn.
Issac Newton discovered the law of gravity in 1687.
Charles Missier discovered the Crab Nebula.
William Herschel discovered the planet Uranus.
Albert developed the Theory of Relativity and that the speed of light in a vacuum was independent of the motion of all others.
Stephen Hawking invented the theory that black holes emit radiation, which is now called Hawking radiation.