Sir W Herschel 1738-1822

Discoverer of the planet Uranus, the intrinsic motion of the Sun, and the form of the Milky Way.

 He came to England in 1757, where he made a living as organist and musician. He secured a fashionable appointment as organist at Bath in 1766 and began to study mathematics and astronomy seriously; by 1774 he had made his own 5½-foot Gregorian reflector. By 1781 he had discovered the planet Uranus, which he first took to be a comet. As soon as its planetary character was known he named it "Georgium Sidus", in honour of the King, who shortly afterwards appointed him Court Astronomer with a salary of £200 a year.

In 1787 Herschel found two satellites of Uranus by the device of omitting the small mirror of his 20-foot telescope and pointing his eyepiece directly at the speculum. His greatest telescope, which was almost 40 feet long and which had an aperture of nearly 50 inches. This instrument was last used in 1811, and Herschel was never able to repolish the mirror adequately, but it remained the largest in existence for half a century.

Herschel's first major discovery in stellar astronomy was that of the intrinsic motion of the Sun through space 1783.

For many years Herschel catalogued double stars, and issued extensive catalogues (1782 and 1785), in the first of which he hinted that many of them might be in relative orbital motion. In 1793 he measured the relative positions of any double stars, and found he had been justified. For the first time in the history of astronomy, Kepler's laws could be applied outside the solar system.

His star-counts had led him to a remarkable picture of the overall form of the Milky Way. His catalogue of 5,000 new nebulae appeared in 1820. This last aspect of his work was not given its proper recognition until this century.

Herschel is remembered also for his discovery of infra-red radiation in the light of the Sun and for some remarkable conjecture as to the properties of this radiation(1800). He maybe said to have created the subject of astronomical colour-photometry.

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