By the 1600s, astronomers had reasoned that comets occur in space, beyond Earth’s atmosphere, and were trying to figure out where a comet’s journey begins and ends. Johannes Kepler (1571–1630), who observed a comet in 1607, concluded that comets follow straight lines, coming from an infinite distance and leaving forever once they passed Earth. Somewhat later, the German astronomer Johannes Hevelius (1611–1687) suggested that comets followed slightly curved paths. In the late 1600s, George Samuel Doerffel (1643–1688) suggested that comets followed a parabolic course. In 1695, Edmund Halley (1656–1742) finally deduced correctly that comets follow highly elliptical orbits around the Sun.