Hevelius, Johannes (1611–1687)

German astronomer. He published the first comparatively detailed map of the Moon in his Selenographia (1647). He also discovered four comets in 1652, 1661, 1672, and 1677, and suggested that these bodies orbited in parabolic paths about the Sun.

His Uranographia contains a catalogue of more than 1,500 stars and a celestial atlas with 54 plates, while Firmamentum Sobiescianum is a star atlas that introduced a number of new constellations. Both were edited by his wife Elizabeth, who assisted him in his work, and published together after his death as Prodromus astronomiae (1690).

Hevelius was born and educated in Danzig (now Gdańsk). He spent some time in Leiden, London, and Paris before settling down in Danzig, where he worked as a brewing merchant and was a city councillor. He spent his evenings on the roof of his house, where he had an observatory installed 1641, and furnished it with instruments of his own construction. He built a number of telescopes using long focal lengths to avoid chromatic aberration, his largest being a tubeless instrument 46 m/150 ft long. Although he used telescopes for details of the Moon and planets, he refused to apply them to his measuring apparatus. His observations of the positions of stars were made with the naked eye, and were more accurate than those of the Danish astronomer Tycho Brahe.

In the period 1642–45 Hevelius deduced a fairly accurate value for the period of the solar rotation, and gave the first description of the bright areas in the neighbourhood of sunspots. The name he gave to them, faculae, is still used.

The observatory was destroyed by fire 1679, with some of his notes.