page_title: William Herschel
section_title: Further discoveries
hierarchical_section_title: William Herschel / Astronomy / Further discoveries
caption_attribution_description: English: "Section of our sidereal system." Herschel, William. "On the Construction of the Heavens. By William Herschel, Esq. FRS." Philosophical Transactions of the Royal Society of London 75 (1785)
context_page_description: Frederick William Herschel, KH, FRS was a German-born British astronomer and composer of music. Frequently he collaborated with his younger sister and fellow astronomer Caroline Lucretia Herschel. Born in the Electorate of Hanover, William Herschel followed his father into the Military Band of Hanover, before emigrating to Great Britain in 1757 at the age of nineteen.
  Herschel constructed his first large telescope in 1774, after which he spent nine years carrying out sky surveys to investigate double stars. Herschel published catalogues of nebulae in 1802 and in 1820. The resolving power of the Herschel telescopes revealed that many objects called nebulae in the Messier catalogue were actually clusters of stars. On 13 March 1781 while making observations he made note of a new object in the constellation of Gemini. This would, after several weeks of verification and consultation with other astronomers, be confirmed to be a new planet, eventually given the name of Uranus. This was the first planet to be discovered since antiquity, and Herschel became famous overnight. As a result of this discovery, George III appointed him Court Astronomer.
context_section_description: In his later career, Herschel discovered two moons of Saturn, Mimas and Enceladus; as well as two moons of Uranus, Titania and Oberon. He did not give these moons their names; they were named by his son John in 1847 and 1852, respectively, after his death. Herschel measured the axial tilt of Mars and discovered that the martian ice caps, first observed by Giovanni Domenico Cassini (1666) and Christiaan Huygens (1672), changed size with that planet's seasons. It has been suggested that Herschel discovered rings around Uranus.
  Herschel introduced but did not create the word "asteroid", meaning star-like (from the Greek asteroeides, aster "star" + -eidos "form, shape"), in 1802 (shortly after Olbers discovered the second minor planet, 2 Pallas, in late March), to describe the star-like appearance of the small moons of the giant planets and of the minor planets; the planets all show discs, by comparison. By the 1850s 'asteroid' became a standard term for describing certain minor planets.
  From studying the proper motion of stars, the nature and extent of the solar motion was first demonstrated by Herschel in 1783, along with first determining the direction for the solar apex to Lambda Herculis, only 10° away from today's accepted position.
  Herschel also studied the structure of the Milky Way and was the first to propose a model of the galaxy based on observation and measurement. He concluded that it was in the shape of a disk, but incorrectly assumed that the sun was in the centre of the disk. This Heliocentric view was eventually replaced by Galactocentrism due to the work of Harlow Shapley, Heber Doust Curtis and Edwin Hubble in the 1900s. All three men used significantly more far-reaching and accurate telescopes than Herschel's.
caption: William Herschel's model of the Milky Way, 1785
exif: {}