How did Tycho Brahe's observations help Johannes Kepler make discoveries?

The collaboration between Johannes Kepler and Tycho Brahe was pivotal for the development of modern astronomy. Kepler initially sought to work with Tycho to obtain more precise planetary data to refine his own cosmological theories.

After Tycho’s death in 1601, Kepler gained access to his extensive collection of observational records. These data were crucial because they were the most accurate measurements available before the invention of the telescope. Specifically, Tycho’s detailed observations of [Mars] were instrumental; because Mars has a significant orbital eccentricity, its motion provided the necessary evidence to reveal that planetary orbits are not circular.

When Kepler found he could not reconcile Tycho’s precise data—which he believed were accurate to within 2 minutes of arc—with traditional circular models, he was forced to abandon those long-held assumptions. This rigorous analysis of Tycho's records led directly to the formulation of Kepler’s laws of planetary motion, which established that planets move in ellipses with the Sun at one focus.12