German astronomer who developed new photographic methods for observational astronomy. He discovered several new nebulae, both within the Milky Way and outside our Galaxy; more than 200 asteroids; and in 1883 a comet, which now bears his name.

Wolf was born and educated in Heidelberg, where he spent most of his career, becoming professor 1893. He used a small private observatory 1885-96, and then became the director of a new observatory at Königstuhl, near Heidelberg, built at his instigation.
Wolf was the first to use time-lapse photography in astronomy, a technique he used for detecting asteroids. In 1903 he discovered the first of the so-called Trojan satellites (number 588, later named Achilles), whose orbits are in precise synchrony with that of Jupiter's; they form a gravitationally stable configuration between Jupiter and the Sun. This kind of triangular three-bodied system had been analysed and predicted theoretically by Joseph Lagrange in the 1770s.
Independently of US astronomer Edward Barnard, Wolf discovered that the dark 'voids' in the Milky Way are in fact nebulae which are obscured by vast quantities of dust, and he studied their spectral characteristics and distribution.
Wolf also was the first to observe Halley's comet when it approached the Earth in 1909.