Tycho Brahe (1546-1601), was a Danish astronomer who made very accurate measurements of the solar system and more than 700 stars. The data Brahe collected was far better than all other measurements made until the invention of the telescope in the early 17th century.

Brahe would split the sky into four different sections and make measurements of the Sun, Moon, stars, and planets. He then recorded the location of the objects in the four sections. By comparing his records from different times, Brahe could compare the locations of objects in the night sky to learn about the movements of those objects.

Brahe studied the stars without special instruments, using only a globe and a pair of compasses. He found many errors in the astronomical tables at the time, and he corrected them. In 1572, he discovered a supernova in the constellation Cassiopeia. Brahe spent more than 20 years observing the stars from his observatory on the island of Hven.

Brahe never fully accepted Copernicus’ sun-centered theory of the universe and tried to combine it with the Ptolemy’s earth-centered system. Brahe proposed that the five known planets revolved around the sun, and the sun (with the planets), circled the earth each year.

Although Brahe's theory was wrong, the measurements and records of his observations played an important role in developing the correct description of how the planets move. Johannes Kepler, who was Brahe's assistant from 1600 until Brahe's death in 1601, used Brahe's data to help him create his three laws of planetary motion.

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