Today in History: March 13,1781 William Herschel discovered the Planet Uranus
Sir Frederick William Herschel, born in Germany on 15 November 1738 as Friedrich Wilhelm Herschel, was a British astronomer , technical expert, and composer.
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| Herschel Museum of Astronomy, music room |
Herschel emigrated to Britain at the age of 19. He composed numerous musical works, concertos, some church music, and 24 symphonies. He played the oboe, cello, harpsichord, and the organ.
His sister Caroline came to England in 1772 and they lived in Bath where their brothers Dietrich, Alexander and Jakob joined them later. William Herschel was appointed director of the Bath orchestra in 1780 and his sister often staged as soprano soloist. Herschel's music led him to an interest in mathematics and lenses.
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| Herschel Museum of Astronomy |
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| Herschel Museum of Astronomy |
He
started building his own reflecting
telescopes and would spend up to 16 hours a day grinding and
polishing the speculum metal primary
mirrors. He "began to look at the planets and the stars"
in May, 1773 and on 1 March 1774 he began an astronomical journal by noting his
observations of Saturn's rings and the Great
Orion Nebula (M 42).
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| Pages from the astronomical journals of William Herschel |
He observed from the back
garden of his house in 19 New King Street, Bath. He used a Newtonian telescope of his own manufacture, in October 1779.
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| Back garden |
Herschel began a
systematic search for "every star in the Heavens".He soon discovered many more binary and multiple stars than expected, and
compiled them with careful measurements of their relative positions in two
catalogues. The catalogues were presented to the Royal
Society in London in 1782 and 1784. In 1821 a third catalogue of discoveries made after 1783 was published. In March, 1781, during his search for double stars,
Herschel noticed an object appearing as a non-stellar disk. Herschel originally thought it was a
comet or a star. He made many more observations of it. The Russian Anders Lexell computed
the orbit and found it to be probably planetary. Herschel determined in agreement that it must be a planet beyond the
orbit of Saturn. He called the new planet the 'Georgian star' (Georgium sidus) after King George III. However, In France, where reference to the
British king was to be avoided if possible, the planet was known as 'Herschel'
until the name 'Uranus' was universally adopted.
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| Herschel Museum of Astronomy |
In 1781 Herschel was awarded the Copley Medal and elected a Fellow of the Royal Society. In 1782, he was appointed "The
King’s Astronomer". He continued his work as a
telescope maker and achieved an international reputation for their manufacture,
profitably selling over 60 completed reflectors to British and Continental
astronomers. During the course of his
career, he constructed more than 400 telescopes.
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| Scale model of the telescope William Herschel constructed. |
The largest and most famous of
these was a reflecting telescope with
a 491⁄2-inch-diameter
(1.26 m) primary mirror and
a 40-foot (12 m) focal length.
This design has come to be called the Herschelian telescope. On 28 August
1789 he discovered a new moon of Saturn and in the following month a second moon.
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| Herschel Museum of Astronomy |
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| Herschel Museum of Astronomy |
In all, Herschel discovered over 800 confirmed double or multiple star systems, almost all of them physical rather than
virtual pairs. His theoretical and observational work provided the foundation
for modern binary star astronomy. In 1783 he gave Caroline a telescope, and she began to make
astronomical discoveries. Caroline discovered 8 comets, 11 nebulae and updated and corrected
Flamsteed's work detailing the position of stars. Her work was published as the British Catalogue of Stars and she was honored by the Royal Astronomical
Society.
Herschel measured the axial tilt of the planet Mars and discovered that the
martian ice caps, first observed
by Giovanni Domenico (1666) and
Christiaan Huygens (1762), changed size with the planet's seasons. From studying the proper
motion of stars, he was the first to realize that the solar system is moving through space, and he determined the
approximate direction of that movement. He also studied the structure of the Milky Way and concluded that it
was in the shape of a disk. William also coined the word asteroid, meaning star-like in 1802 . However,
it was not until the 1850s that 'asteroid' became a standard term for
describing certain minor planets.
All photos ( by Ticia Verveer) in this blog article are taken in The Herschel Museum of Astronomy which is situated in the Herschels' former home at 19 New King Street in Bath, England .
Uranus was the first planet found with the aid of a telescope.
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Herschel Museum of Astronomy
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