Herschel, F. Wilhelm

Friedrich Wilhelm Herschel was born in Hannover November, 15th 1738 to his father Isaak Herschel and his mother Anna Ilse Moritzen. His father was a military musician. Isaak and his wife had ten children, four died very young. the other five, beside Friedrich Wilhelm, were Sophia Elisabeth, born April, 12th 1733; Heinrich Anton Jakob, born November 20st 1734; Johann Alexander, November 13th 1745; Karoline Lucretia, March 16th 1750 and Johann Dietrich, September 13th 1755.

Friedrich Wilhelms father founded the interest in astronomy at early years with talks at the fireside and visual observations. Also, every child was taught to play an instrument. From May, 1st 1753, after school, Wilhelm played in the same military music orchestra as his father. In 1756 the regiment was sent to England for some months where he learned the language quickly. After a battle in Germany Friedrich Wilhelm and his brother Jakob went to Hamburg for a ship to England, where they planned to earn a living as musicians. After Jakobs return to Hannover, Wilhelm went to Richmond to play in the orchestra of the Earl of Darlington. 1762 he moved to Leeds, he stayed for four years, then leaving for Halifax for some months. On December 9th 1766 he again moved, now to Bath. Here he should stay for 15 years. He rented a house with friends from Leeds, the Bulmans, at Beaufort Square. On October, 4th 1767 he started his new career as an organist at the privately owned Octagon church. This building still exists and is today (1994) used as a showroom of the Royal Photographic Society. In the summer of 1772 Wilhelm Herschel went to Hannover to help his sister Karoline with the travel to Bath, where she got an education as a singer.

In 1773 Wilhelm Herschels interest in astronomy suddenly grew. He read books on astronomy and bought instruments and lenses. His first telescope seems to have been an reflector of the Gregory design. But it was too small and did not satisfy him. Herschel liked a bigger instrument, but good lenses were expensive. So he had the idea of making his own mirrors. From a man in Bath he bought the equipment for pouring the metal, grinding and polishing tools and some already ground disks.

1774 Friedrich Wilhelm and his sister Karoline moved to Walcott Turnpike, just outside of Bath. This house had a flat roof that was used as an observing platform. 1777 they again changed their residence, now to New King Street, which was closer to the town centre. More and more often his pupils asked to learn not only about music, but also about astronomy. Residents and visitors of Bath asked him to have a look through his instruments. One evening the Astronomer Royal and director of the Greenwich observatory, Maskelyne, visited him, starting a long lasting friendship.

In 1779 the Herschels again moved to another place in Bath, now to 5, River Street. The reason for this is not known, the house had no garden and was unsuitable for telescope work. So Wilhelm one evening placed his telescope on the street right beside the house, when a man passing by asked to have a view of the moon. The other morning this man visited again and introduced himself as Dr William Watson, member of the Royal Society and founder of a philosophical society in Bath. He invited Herschel to join this society. Between 1779 and 1781 W. Herschel had measured the heights of about a hundred moon mountains, writing down his results. These papers were his first presented to the Royal Society by Dr Watson.

On the evening of March, 13th 1781 Herschel was working on the extension of his double star catalog when he found a bright object in an area near the star H Geminorum where the charts of Harris showed no star. Herschel suspected a comet. Observations the following nights showed a slow moving object. He reported this to Maskelyne and to Dr. Hornsby, the director of Oxford observatory. Maskelyne suggested an unknown planet while Herschel and Hornsby thought it was a comet. After collecting enough material for calculations, Lexell in St. Petersburg and Laplace in France found an orbit for a planet at twice the distance of Saturn. A new planet was found.

In November 1781 Herschel was invited to London by the Royal Society and received the Copley medal from Sir Joseph Banks, president of the society. On December 7th Herschel was informed that he was elected Fellow of the Royal Society.

At the end of May 1782 Herschel left Bath for London on an invitation of King George III. He showed the royal family several planets during June and July and was offered the position of court astronomer at Windsor for an annual sum of 200 pounds. His sister was paid 50 pounds for assisting him. Herschel named the new found planet 'Georgium sidus', Georges star. Later the name Uranus, proposed by Galle in Berlin, was used by the astronomers while Herschel referred to 'Georgium sidus' all his life.

On August, 2nd 1782 Herschels instruments arrived from Bath at his house in Datchet near Windsor where he immediately started observing again. By 1784 he presented his second catalog on 434 additional double stars to the Royal Society. In Datchet he started to build telescopes to sell them. His experimental work and frequent travels to London were not covered by the money he got from the king. The high quality of his optics was soon well known outside of England and he received orders from foreign countries. The income from this soon was higher than the 200 pounds he earned for his court astronomer post. His list of customers include the King of Spain, the Prince of Canino, the Russian court and the Austrian Emperor. He also made telescopes for Bode in Berlin, Schröter, Piazzi and Pond. One instrument was sold to China.

Between 1786 and 1802 Wilhelm Herschel published three catalogues containing data on 2500 nebular objects. The observations for these were mostly done with the "20-feet telescope", an instrument with 20 feet focal length and 18.8 inch diameter. In June 1785 the Herschels moved again, first to "Clay Hall", a house near Windsor, than in April 1786 to Slough. Here Herschel started to build his biggest telescope, the "40 feet". The first observations were made on February, 19th 1787, but Herschel was not satisfied with the figure of the mirror: it was too thin and bent under its own weight of 1000 pounds. He ordered a new disk to be poured, but it broke during the cooling process. The third disk was a success. With 3.5 inch it was twice as thick as the first one and had a diameter of 48 inch. It weighed 2000 pounds. This mirror had 'first light' on August, 28th 1789, when Herschel observed Saturn with it and soon found the sixth moon of Saturn, Enceladus. On September 17th he found Mimas, the seventh satellite of Saturn. This big instrument never got to be his favorite telescope for several reasons: the mirror needed repolishing very often and the tube was difficult to handle. Herschel preferred to observe with the 20-feet telescope, with which he discovered the Uranus moons Titania and Oberon. A piece of the 40-feet telescope tube is now on display in the garden of Greenwich observatory, covered under an aluminium-and-glass construction. The mirror seems to be lost.

On May, 8th 1788 Wilhelm Herschel, at the age of 50, married Mrs. Mary Pitt, widow in Upton. Their son John Frederick William was born on March 7th, 1792. The work went on and in the following years Wilhelm published several papers. In 1802 he proposed the name "Asteroids" for the new objects discovered by Piazzi and Olbers.

In 1820 the Royal Astronomical Society was founded and Herschel was elected vice president and than president a year later.

Herschels last published paper was a catalog of 145 double stars, dated 1821. One of his last observations was made on July, 4th 1819, when he observed a comet. He died on August, 25th 1822, aged 84.

Beside his astronomical work Herschel composed music. Some of it is available on CD from: Disques DOM, 4-6 rue du Donjon, 94300 Vincennes, France. It was produced in 1992, the interpret Dominique Proust is astrophysicist at the Observatory in Meudon.

1. BUTTMANN, G., Wilhelm Herschel, WVG Stuttgart 1961
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