Brahe's model of the universe can be explained best with this model below.
(p.409, Dictionary of Scientific Biography)
In this model, Brahe describes the universe with the earth at the center.The sun orbits the earth while the other planets revolve around the sun in the order of Mercury, Venus, Mars, Jupiter, and Saturn.There is also a realm of fixed stars beyond the paths of the planetary orbits.In contradiction with the traditional Aristotelian view of the universe, Brahe believed the heavens were imperfect and could be changed.
Brahe's model of the universe wasfirst worked out by 1583 and printed in 1588 in De mundi aetherei recentioribus phaenomenis, however, his model was never presented in great detail.
In spite of his extremely precise observations, Brahe could not detect a parallax for even a single star.If the Earth did in fact orbit the Sun, the stars would have to be infinitely distant.Brahe could not conceive of a universe so immense that an observer as accurate as himself could not detect any stellar parallax.
Even more convincing to Tycho was the fact that he believed he could measure the angular size of stars.The brightest of them he thought to be 2 arcminutes across.The farther away an object is, the larger its true size must be in order that it have a given angular diameter.Brahe could not detect as much as 1 arcminute of parallax for any star, so he concluded that stars were so distant that, to have angular diameters of 2 arcminutes, they actual sizes would have to be twice the size of the entire orbit of the Earth.If they were still farther away, their diameters would have to be proportionally greater(Abell, Morriso, and Wolff 35).
In 1572, Brahe observed a supernova in the constellation of Cassiopeia where no star had been seen before.The prevailing opinion held that the supernova was not really a