Tycho Brahe 14 December 1546 – 24 October 1601Tycho Brahe, in the 1570's had proposed a geo-heliocentric model of the unverse. His belief was that the earth WAS the center of the universe and that the sun orbited around the earth. But what separated this idea from other non-heliocentric ideas, was that the other plants in this model orbited the sun still. Brahe tested his model by searching for Stellar Parallax, which he couldn't find. Thus proving his model, but only due to the lack of new technology required for this paradigm shift.
Tycho Brahe 14 December 1546 – 24 October 1601Tycho Brahe took note of a celestial object that was not present prior within the constellation of Cassiopeia. This was a significant find, as the telescope had yet to be invented and used (Galileo Galilei in 1609). This find was done using the naked eye and any other instruments that Tycho Brahe constructed himself. Another reason for this event's significance was due to the find challenging the current view of the "unchanging" heavens, which he published.
Brahe, Tycho. De Nova Stella. 1573.
Tycho Brahe 14 December 1546 – 24 October 1601Tycho Brahe was one of the observers of the Great Comet of 1577. Brahe, after his observation of the comet, noticed in his findings that the comet was further away than the moon was to earth. He also had noticed that there was no measurable parallax for the celestial object. These two discoveries also challenged the current held view of an unchanging heavens that dominated common knowledge at the time. It also proved Aristotle's theory wrong, showing that comets are actual astronomical events.
Tycho Brahe 14 December 1546 – 24 October 1601/ Johannes Kepler 27 December 1571 - 15 November 1630One final large contribution made by Tycho Brahe was actually posthumous. His apprentice Johannes Kepler rigorously studied Brahe's findings made throughout his life, especially those regarding planetary motion. This resulted in Johannes Kepler being able to create his book "Astronomia Nova" (1609), which described his (at the time) two laws of planetary motion.
Kepler, Johannes. Astronomia Nova. 1609.
Tycho Brahe 14 December 1546 – 24 October 1601