Kepler, using precise eyeball observations made by TychoBrahe?, discovered the three laws of planetary movement that carry his name (though he published then mixed with some other not-so-correct ideas, and did't give them the importance that we do).
Galilei was apparently the first one to use the TeleScope to observe the sky, discovering the moons of JupiTer? and the SunSpot?s, but he is most famous by his problems with the CatholicChurch? (the story usually known is just a cartoon a the real thing). Galileo's greatest contribution to science was not in astronomy, but in dynamics, where he studied the motion of objects.
IsaacNewton? was the first one to marry physics with astronomy, discovering that the same force that causes objects to fall on earth, causes the motion of planets and the moon. Using his LawOfGravity?, the LawsOfKepler? are explained, and the heliocentric system gains a sound physical basis. Newton also found out that the white light from the sun can be decomposed into its component colors, this fact is crucial for most of the 20th century research.
At the end of the 19th century it was discovered that, when decomposing the light from the sun, multitude of SpectralLines? were observed (regions where there was less or no light). Experiments with hot gases showed that the same lines could be observed in the spectra of gases, specific lines corresponding to unique elements. It was proved that the ElementS? found on the sun were also found on earth.
During the 20th century SpectroMetry? (the study of these lines) advanced.
(to be continued)
Most of our current knowledge was gained during the 20th century. With the help of the use of PhotoGraphy?, fainter objects were observed. Our sun was found to be part of a Galaxy made by more than 10^10 stars, and the existence of other galaxies like our own, at large distances at receiding from our own, was confirmed.