Tycho Brahe was born to an aristocratic Danish family in southern Sweden. He studied law and astronomy at the University of Copenhagen and then went on a study tour of Europe in 1562. Back in Sweden, he built a castle and observatory called Uraniborg (after Urania, the Greek goddess of the sky) on the family's island of Hven. There he and his younger sister Sophia, who served as his assistant and student, recorded detailed observations on the positions of planets and stars, and made computations to predict comets and eclipses. In 1588, he published the first volume of the monumental two-part work Astronomiae Instauratae Progymnasmata (Introduction to the New Astronomy). In 1597, Brahe went to Wandsbech near Hamburg in present-day Germany. He eventually settled in Prague, where he continued his astronomical observations. Brahe's observations supported the heliocentric theory that had been proposed earlier by Copernicus, and he proved that comets were not just components of Earth's atmosphere, but objects traveling through space. He also invented instruments such as the Tyconian Quadrant, which were widely copied and led to the invention of improved astronomical equipment. He hired Johannes Kepler as his assistant in 1600; in later years, Kepler would use Brahe's work as the basis for the laws of planetary movement.