Kepler's plot of Halley's Comet, 1607. The Sun is at upper right, while the supposedly straight line followed by the comet is shown from 23 September (lower right) to 26 October (upper left). The orbits and Latin names of three planet are also shown: Earth (Tellur), Venus (Veneris) and Mercury (Mercuris). This diagram was published in the book De Cometis Libelli Tres (1619) by the German astronomer Johannes Kepler (1571-1630). This data was used by the English astronomer Edmond Halley in 1705 to identify this sighting of the comet as one of many made over the centuries as it returns roughly every 75 years.