William Herschel

Frederick William Herschel ( ; ; 15 November 1738 – 25 August 1822) was a German–British astronomer and composer. He frequently collaborated with his younger sister and fellow astronomer Caroline Herschel. Born in the Electorate of Hanover, he followed his father into the military band of Hanover, before emigrating to Britain in 1757 at the age of 19.

Taking an interest in astronomy in 1766, 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 (2,500 objects) and in 1820 (5,000 objects). 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. He was elected a Fellow of the Royal Society and grants were provided for the construction of new telescopes.

Herschel pioneered the use of astronomical spectrophotometry, using prisms and temperature measuring equipment to measure the wavelength distribution of stellar spectra. In the course of these investigations, Herschel discovered infrared radiation.

Other work included an improved determination of the rotation period of Mars, (for which he was pardoned by George III in 1782). Wilhelm, nineteen years old at this time, was a quick student of English. In England, he anglicised his name to Frederick William Herschel.

thumb|right|Original manuscript of Symphony No. 15 in E-flat major (1762)

thumb|Plaque at the [[Herschel Museum of Astronomy, which was the family home at 19 New King Street, Bath]]

In addition to the oboe, he played the violin and harpsichord and later the organ. He composed numerous musical works, including 24 symphonies and many concertos, as well as some church music. Six of his symphonies were recorded in April 2002 by the London Mozart Players, conducted by Matthias Bamert (Chandos 10048).

He was head of the Durham Militia band from 1760 to 1761. Herschel moved to Sunderland in 1761; Charles Avison engaged him as the first violin and soloist for his Newcastle orchestra, where he played for one season. In "Sunderland in the County of Durh: apprill 20th 1761" he wrote his Symphony No. 8 in C Minor. He visited the home of Sir Ralph Milbanke at Halnaby Hall near Darlington in 1760, where he wrote two symphonies, as well as giving performances himself.

After Newcastle, he moved to Leeds and Halifax where he was the first organist at St John the Baptist church (now Halifax Minster).

In 1766, Herschel became organist of the Octagon Chapel, Bath, a fashionable chapel in a well-known spa, in which city he was also Director of Public Concerts. He was appointed as the organist in 1766 and gave his introductory concert on 1 January 1767. As the organ was still incomplete, he showed off his versatility by performing his own compositions including a violin concerto, an oboe concerto, and a harpsichord sonata. On 4 October 1767, he performed on the organ for the official opening of the Octagon Chapel.

His sister Caroline arrived in England on 24 August 1772 to live with William in New King Street, Bath. Herschel's brothers Dietrich, Alexander and Jakob also appeared as musicians of Bath. In 1780, Herschel was appointed director of the Bath orchestra, with his sister often appearing as soprano soloist.

Herschel's intellectual curiosity and interest in music eventually led him to astronomy, making his first recorded observation in 1766. After reading Robert Smith's Harmonics, or the Philosophy of Musical Sounds (1749), he took up Smith's A Compleat System of Opticks (1738), which described techniques of telescope construction. He also read James Ferguson's Astronomy explained upon Sir Isaac Newton's principles and made easy to those who have not studied mathematics (1756) and William Emerson's The elements of trigonometry (1749), The elements of optics (1768) and The principles of mechanics (1754). in May 1773 and on 1 March 1774 began an astronomical journal by noting his observations of Saturn's rings and the Great Orion Nebula (M42).

By 1779, Herschel had also made the acquaintance of Sir William Watson, who invited him to join the Bath Philosophical Society. A few years later, in 1785, Herschel was elected an international member of the American Philosophical Society in Philadelphia.

Double stars

Herschel's early observational work soon focused on the search for pairs of stars that were very close together visually. Astronomers of the era expected that changes over time in the apparent separation and relative location of these stars would provide evidence for both the proper motion of stars and, by means of parallax shifts in their separation, for the distance of stars from the Earth. The latter was a method first suggested by Galileo Galilei.

From the back garden of his house in New King Street, Bath, and using a , (f/13) Newtonian telescope "with a most capital speculum" of his own manufacture, in October 1779, Herschel began a systematic search for such stars among "every star in the Heavens", and 1784 (434 systems). A third catalogue of discoveries made after 1783 was published in 1821 (145 systems).

The Rev. John Michell of Thornhill published work in 1767 on the distribution of double stars, and in 1783 on "dark stars", that may have influenced Herschel. After Michell's death in 1793, Herschel bought a ten-foot-long, 30-inch reflecting telescope from Michell's estate.

In 1797, Herschel measured many of the systems again, and discovered changes in their relative positions that could not be attributed to the parallax caused by the Earth's orbit. He waited until 1802 (in Catalogue of 500 new Nebulae, nebulous Stars, planetary Nebulae, and Clusters of Stars; with Remarks on the Construction of the Heavens) to announce the hypothesis that the two stars were "binary sidereal systems" orbiting under mutual gravitational attraction, a hypothesis he confirmed in 1803 in his Account of the Changes that have happened, during the last Twenty-five Years, in the relative Situation of Double-stars; with an Investigation of the Cause to which they are owing. double or multiple star systems, almost all of them physical rather than optical pairs. His theoretical and observational work provided the foundation for modern binary star astronomy;

Uranus

thumb|[[Uranus, discovered by Herschel in 1781]]

In March 1781, during his search for double stars, Herschel noticed an object appearing as a disk. Herschel originally thought it was a comet or a stellar disc, which he believed he might actually resolve. He reported the sighting to Nevil Maskelyne the Astronomer Royal. He made many more observations of it, and afterwards Finnish-Swedish astronomer Anders Lexell computed the orbit and found it to be probably planetary.

Herschel agreed, determining 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, which also brought him favour; the name did not stick. The same year, Herschel was awarded the Copley Medal and elected a Fellow of the Royal Society.

On 1 August 1782 Herschel and his sister Caroline moved to Datchet (then in Buckinghamshire but now in Berkshire). There, he continued his work as an astronomer and telescope maker. He achieved an international reputation for their manufacture, profitably selling over 60 completed reflectors to British and Continental astronomers.

Deep sky surveys

thumb|[[NGC 2683 is an unbarred spiral galaxy discovered by William Herschel on 5 February 1788.]]

From 1782 to 1802, and most intensively from 1783 to 1790, Herschel conducted systematic surveys in search of "deep-sky" or non-stellar objects with two , telescopes (in combination with his favoured 6-inch-aperture instrument). Excluding duplicated and "lost" entries, Herschel ultimately discovered over 2,400 objects defined by him as nebulae.)

Herschel published his discoveries as three catalogues: Catalogue of One Thousand New Nebulae and Clusters of Stars (1786), Catalogue of a Second Thousand New Nebulae and Clusters of Stars (1789) and the previously cited Catalogue of 500 New Nebulae ... (1802). He arranged his discoveries under eight "classes": (I) bright nebulae, (II) faint nebulae, (III) very faint nebulae, (IV) planetary nebulae, (V) very large nebulae, (VI) very compressed and rich clusters of stars, (VII) compressed clusters of small and large [faint and bright] stars, and (VIII) coarsely scattered clusters of stars. Herschel's discoveries were supplemented by those of Caroline Herschel (11 objects) and his son John Herschel (1754 objects) and published by him as General Catalogue of Nebulae and Clusters in 1864. This catalogue was later edited by John Dreyer, supplemented with discoveries by many other 19th-century astronomers, and published in 1888 as the New General Catalogue (abbreviated NGC) of 7,840 deep-sky objects. The NGC numbering is still the most commonly used identifying label for these celestial landmarks.

In October 1783, a new 20-foot telescope came into service for William. During this time, William was attempting to observe and then record all of the observations. He had to run inside and let his eyes readjust to the artificial light before he could record anything, and then he would have to wait until his eyes were adjusted to the dark before he could observe again. Caroline became his recorder by sitting at a desk near an open window. William would shout out his observations and she would write them down along with any information he needed from a reference book.

Caroline began to make astronomical discoveries in her own right, particularly comets. In 1783, William built her a small Newtonian reflector telescope, with a handle to make a vertical sweep of the sky. Between 1783 and 1787, she made an independent discovery of M110 (NGC 205), which is the second companion of the Andromeda Galaxy. Between 1786 and 1797, she discovered or observed eight comets. and, at her brother's suggestion, updated and corrected Flamsteed's work detailing the position of stars. She also rediscovered Comet Encke in 1795.

The Catalogue of stars taken from Mr Flamsteed's observations contained an index of more than 560 stars that had not been previously included.

For her work as William's assistant, she was granted an annual salary of £50 by George III. Her appointment made her the first female in England to be honoured with a government position. It also made her the first woman to be given a salary as an astronomer.

In June 1785, owing to damp conditions, William and Caroline moved to Clay Hall in Old Windsor. On 3 April 1786, the Herschels moved to a new residence on Windsor Road in Slough. It was demolished in 1963.

William Herschel's marriage in 1788 caused considerable tension in the brother–sister relationship. Caroline has been referred to as a bitter, jealous woman who worshipped her brother and resented her sister-in-law for invading her domestic life. With the arrival of Mary, Caroline lost her managerial and social responsibilities in the household, and with them much of her status. Caroline destroyed her journals between the years 1788 to 1798, so her feelings during this period are not entirely known. According to her memoir, Caroline then moved to separate lodgings, but continued to work as her brother's assistant. When her brother and his family were away from their home, she would often return to take care of it for them. In later life, Caroline and Lady Herschel exchanged affectionate letters. In 1828, she was awarded the Gold Medal of the Royal Astronomical Society for her work.

Herschel's telescopes

The most common type of telescope at that time was the refracting telescope, which involved the refraction of light through a tube using a convex glass lens. This design was subject to chromatic aberration, a distortion of an image due to the failure of light of different component wavelengths to converge. Optician John Dollond tried to correct for this distortion by combining two separate lenses, but it was still difficult to achieve good resolution for far distant light sources.

The creation of larger, symmetrical mirrors was extremely difficult. Any flaw would result in a blurred image. Because no one else was making mirrors of the size and magnification desired by Herschel, he determined to make his own. Herschel and his assistants built and sold at least sixty complete telescopes of various sizes.

thumb|A [[Cassini-Huygens|Cassini orbiter's view of Mimas, a moon of Saturn discovered by Herschel in 1789]]

In 1789, shortly after this instrument was operational, Herschel discovered a new moon of Saturn: Mimas, only in diameter. Discovery of a second moon (Enceladus) followed, within the first month of observation.

William Herschel was disappointed with it.

Most of Herschel's observations were done with a smaller , reflector. Nonetheless, the 40-foot caught the public imagination. It inspired scientists and writers including Erasmus Darwin and William Blake, and impressed foreign tourists and French dignitaries. King George was pleased.

Reconstruction of the 20-foot telescope

In 2012, the BBC television programme Stargazing Live built a replica of the 20-foot telescope using Herschel's original plans but modern materials. It is to be considered a close modern approximation rather than an exact replica. A modern glass mirror was used, the frame uses metal scaffolding and the tube is a sewer pipe. The telescope was shown on the programme in January 2013 and stands on the Art, Design, and Technology campus of the University of Derby where it will be used for educational purposes.

Life on other celestial bodies

Herschel was sure that he had found ample evidence of life on the Moon and compared it to the English countryside.

Herschel went so far as to speculate that the interior of the Sun was populated. Over a period of 40 years (1779–1818), Herschel regularly observed sunspots and their variations in number, form and size. Most of his observations took place in a period of low solar activity, the Dalton Minimum, when sunspots were relatively few in number. This was one of the reasons why Herschel was not able to identify the standard 11-year period in solar activity.

Herschel compared his observations with the series of wheat prices published by Adam Smith in The Wealth of Nations.

In 1801, Herschel reported his findings to the Royal Society and indicated five prolonged periods of few sunspots correlated with the price of wheat. and the significance of the correlation is doubted by some scientists.

Further discoveries

{| style="float:right; border:1px solid #ccc; margin-left:15px;" cellpadding="5"

|+ Planets discovered: 1

| Uranus || 13 March 1781

{| style="float:right; border:1px solid #ccc; margin-left:15px;" cellpadding="5"

|+ Moons discovered: 4

| Oberon || 11 January 1787

| Titania || 11 January 1787

| Enceladus || 28 August 1789

| Mimas || 17 September 1789

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. 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.

thumb|right| William Herschel's model of the Milky Way, 1785

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 20th century. All three men used significantly more far-reaching and accurate telescopes than Herschel's.

Discovery of infrared radiation in sunlight

In early 1800, Herschel was testing different filters to pass sunlight through, and noticed that filters of different colours seemed to generate varying amounts of heat. He decided to pass the light through a prism to measure the different colours of light using a thermometer, He published these results in April 1800.

Biology

Herschel used a microscope to establish that coral was not a plant – as many at the time believed – because it lacked the cell walls characteristic of plants. It is in fact an animal, a marine invertebrate.

Family and death

thumb|William Herschel's coat of arms deemed a notorious example of [[debased heraldry: Argent, on a mount vert a representation of the 40 ft. reflecting telescope with its apparatus proper on a chief azure the astronomical symbol of Uranus irradiated or. Crest: A demi terrestrial sphere proper thereon an eagle, wings elevated or]]

On 8 May 1788, Herschel married the widow Mary Pitt (née Baldwin) at St Laurence's Church, Upton in Slough. They had one child, John, born at Observatory House on 7 March 1792. Herschel's personal background and rise as man of science had a profound impact on the upbringing of his son and grandchildren. He was elected a Foreign Honorary Member of the American Academy of Arts and Sciences in 1788. In 1816, William was made a Knight of the Royal Guelphic Order by the Prince Regent and was accorded the honorary title 'Sir' although this was not the equivalent of an official British knighthood.

Herschel received British citizenship in 1793.

He helped to found the Astronomical Society of London in 1820, which in 1831 received a royal charter and became the Royal Astronomical Society. In 1813, he was elected a foreign member of the Royal Swedish Academy of Sciences.

On 25 August 1822, Herschel died at Observatory House, Windsor Road, Slough, Buckinghamshire, after a long illness. Caroline was deeply distressed by his death, and soon after his burial she returned to Hanover, a decision she later regretted. She had lived in England for fifty years. Her interests were much more in line with her nephew John Herschel, also an astronomer, than with her surviving family in Hanover. She continued to work on the organization and cataloguing of nebulae, creating what would later become the basis of the New General Catalogue. She died on 9 January 1848.

Memorial

William Herschel lived most of his life in the town of Slough, then in Buckinghamshire (now in Berkshire). He died in the town and was buried under the tower of the nearby St Laurence's Church, Upton-cum-Chalvey. Herschel's epitaph is:

thumb|upright|Statue of William and Caroline in the garden of the [[Herschel Museum of Astronomy in Bath where William discovered Uranus]]

Herschel is especially honoured in Slough and there are several memorials to him and his discoveries. In 2011 a new bus station, the design of which was inspired by the infrared experiment of William Herschel, was built in the centre of Slough. There is a commemorative plaque of Herschel installed by the Institute of Physics in London. There is a memorial plaque of William near the choir screen in Westminster Abbey.

Musical works

Herschel's complete musical works are as follows:

18 symphonies for small orchestra (1760–1762)
6 symphonies for large orchestra (1762–1764)
12 concertos for oboe, violin and viola (1759–1764)
2 concertos for organ
6 sonatas for violin, cello and harpsichord (published 1769)
12 solos for violin and basso continuo (1763)
24 capriccios and 1 sonata for solo violin
1 andante for two basset horns, two oboes, two horns and two bassoons.

Various vocal works including a "Te Deum", psalms, motets and sacred chants along with some catches.

Keyboard works for organ and harpsichord:

6 fugues for organ
24 sonatas for organ (10 now lost)
33 voluntaries and pieces for organ (incomplete)
24 pieces for organ (incomplete)
12 voluntaries (11 now lost)
12 sonatas for harpsichord (9 extant)
25 variations on an ascending scale
2 minuets for harpsichord

Named after Herschel

thumb|The [[William Herschel Telescope in La Palma. Funded by research councils from the UK, the Netherlands and Spain, it was built in 1987.]]

The astrological symbol for planet Uranus (22px) features the capital initial letter of Herschel's surname.
Mu Cephei is also known as Herschel's Garnet Star
Herschel, a crater on the Moon
Herschel, a large impact basin on Mars
The enormous crater Herschel on Saturn's moon Mimas
The Herschel gap in Saturn's rings.
2000 Herschel, an asteroid
The William Herschel Telescope on La Palma
The Herschel Space Observatory, successfully launched by the European Space Agency on 14 May 2009. It was the largest space telescope of its kind, until the launch of the James Webb Space Telescope.
Herschel Grammar School, Slough
Rue Herschel, a street in the 6th arrondissement of Paris.
The Herschel Building at Bath College, Bath
The Herschel building at Newcastle University, Newcastle, United Kingdom
Herschel Museum of Astronomy, at 19 New King Street in Bath.
Herschelschule, Hanover, Germany, a grammar school
The Herschel Observatory, at the Universitas School in Santos, Brazil.
The lunar crater C. Herschel, the asteroid 281 Lucretia, and the comet 35P/Herschel-Rigollet are named after his sister Caroline Herschel.
The public house "Herschel Arms" at 22 Park Street, Slough is named after him and is quite close to the site of Observatory House.
Herschel Astronomical Society, the operator of the Herschel Memorial Observatory based in Eton, Berkshire.
Herschel Park, Slough.
The shape of Slough Bus Station, built in 2011, was inspired by Herschel's infrared experiment.
Herschel Street, a street in Brisbane, Australia.

Brothers and sisters

Sophia Elizabeth Herschel (1733–1803) – in 1755 married violinist Johann Heinrich Griesbach (1730–1773), she lived in Hannover all her life, and had seven children.
(1734–1792) – musician, unmarried
Johann Heinrich Herschel (1736–1743)
Anna Christina Herschel (1741–1748) – died of whooping cough.
Johann Alexander Herschel (1745–1821) – he was married to Margarethe Smith, no children.
Maria Dorothea Herschel (1748–1749)
Caroline Lucretia Herschel (1750–1848)
Franz Johann Herschel (1752–1754) – died from smallpox.
Johann Dietrich Herschel (1755–1827) – musician, he married Catharina Maria Reiff (1760–1846) and had four children.

References

Sources

External links

Articles and letters published in the Philosophical Transactions and available online (70 items, June 2016)
William Herschel's Deep Sky Catalog
The William Herschel Double Star Catalogs Restored
Full text of
Full text of The Story of the Herschels (1886) from Project Gutenberg
Portraits of William Herschel at the National Portrait Gallery (United Kingdom)
Herschel Museum of Astronomy located in his Bath home
William Herschel Society
The Oboe Concertos of Sir William Herschel, Wilbert Davis Jerome ed.
A notebook of Herschel's, dated from 1759 is available in the digital collections of the Linda Hall Library.
Portraits of William Herschel (and other members of the family) from the Lick Observatory Records Digital Archive, UC Santa Cruz Library's Digital Collections
Michael Lemonick: William Herschel, the First Observational Cosmologist, 12 November 2008, Fermilab Colloquium
Musical pieces by William Herschel @YouTube:
(Chamber Symphony in F, 2nd movement)