William Herschel

German-British astronomer and composer Frederick William Herschel KH, FRS (/ˈhɜːrʃəl/; German: Friedrich Wilhelm Herschel; 15 November 1738 – 25 August 1822). He worked closely with Caroline Herschel, his younger sister, and a fellow astronomer, on several occasions. William Herschel, who was born in the Electorate of Hanover, joined his father in the Hanoverian military at the age of nineteen and immigrated to Great Britain in 1757.

After building his first huge telescope in 1774, Herschel conducted sky surveys to look at double stars for nine years. Two catalogs of nebulae, including 2,500 objects each, were released by Herschel in 1802 and 1820, respectively.

Numerous objects in the Messier catalog that were labeled as nebulae turned out to be star clusters thanks to the Herschel telescopes’ remarkable resolving capabilities. During his observations on March 13, 1781, he noticed a new object in the Gemini constellation. After a few weeks of investigation and discussion with other astronomers, this would be determined to be a new planet and subsequently given the name Uranus. Herschel gained instant fame after discovering this planet, which was the first to be found since antiquity.

Following this finding, he was named Court Astronomer by George III. Grants were given for the building of further telescopes, and he was made a Fellow of the Royal Society.

Herschel was a pioneer in the field of astronomical spectrophotometry, measuring the wavelength distribution of star spectra with prisms and temperature measurement apparatus. Herschel discovered infrared radiation during these observations. Additional research yielded improved Mars rotation period determinations, seasonal variations in the Martian polar caps, and the discoveries of Titania and Oberon (moons of Uranus) and Enceladus and Mimas (moons of Saturn). In 1816, Herschel received the title of Knight of the Royal Guelphic Order. When the Royal Astronomical Society was established in 1820, he served as its first president. Following his death in August 1822, his lone son John Herschel carried on his father’s work.

Childhood and musical pursuits

One of ten children born to German Lutheran immigrant Isaak Herschel and his wife Anna Ilse Moritzen, Herschel was born in the Electorate of Hanover, Germany, which was then a part of the Holy Roman Empire. His ancestors were from Saxony, namely Pirna. Hamel has questioned theories that they were Protestants from Bohemia because the Herschel surname was already present in the same area where the family resided a century earlier.

Herschel’s dad performed with the Hanover Military Band as an oboist. Wilhelm and his brother Jakob were oboists in the Hanoverian Guards regiment when they were deployed to England in 1755. King George II was the unifying force behind the crowns of Hanover and Great Britain at that time. Recalled from England to defend Hanover, the Hanoverian Guards faced impending conflict with France.

In the latter part of 1757, Herschel’s father Isaak dispatched his two boys to England in search of safety following their defeat at the Battle of Hastenbeck. Wilhelm was charged with desertion despite the fact that his elder brother Jakob had been fired from the Hanoverian Guards; George III pardoned him for this offense in 1782).

Wilhelm, who was nineteen at the time, picked up the English language quickly. He was known by his English name, Frederick William Herschel when he was in England.

He played the organ later on in addition to the oboe, violin, and harpsichord. Along with some religious pieces, he wrote a great deal of music, including 24 symphonies and several concertos.

The London Mozart Players, under the direction of Matthias Bamert, recorded six of his symphonies in April 2002 (Chandos 10048).

From 1760 to 1761, he led the Durham Militia band. After relocating to Sunderland in 1761, Herschel spent a season playing as the first violin and soloist for Charles Avison’s orchestra in Newcastle. His Symphony No. 8 in C Minor is described in “Sunderland in the County of Durh: apprill [sic] 20th 1761”. In 1760, he went to Sir Ralph Milbanke’s house at Halnaby Hall, close to Darlington, where he composed two symphonies and gave performances of his own. He relocated to Leeds and Halifax after leaving Newcastle, where he served as the church’s first organist at St. John the Baptist (now Halifax Minster).

Herschel was appointed organist of Bath’s Octagon church in 1766, a posh church in a renowned spa where he also served as Director of Public Concerts. On January 1, 1767, he delivered his inaugural concert after being named organist in 1766. He demonstrated his flexibility by playing his own works, which included a harpsichord sonata, an oboe concerto, and a violin concerto, while the organ was still unfinished.

He played an organ concert at the Octagon Chapel’s official opening on October 4, 1767.

On August 24, 1772, his sister Caroline left for England to live with William in New King Street, Bath. The Herschel Museum of Astronomy is currently housed in the home they shared. Bath’s musicians included Herschel’s brothers Dietrich, Alexander, and Jakob (1734–1792). Herschel became the Bath orchestra’s director in 1780, and his sister frequently sang as a soprano soloist.

Astronomy

Herschel’s readings in natural philosophy in the 1770s reveal not just his own preferences but also his desire to advance in both his social and professional life. He was in a good position to interact with philomaths, or “philosophical Gentlemen,” of various logical and pragmatic inclinations in the eighteenth century. Herschel later became interested in astronomy due to his intellectual curiosity and love of music. He started with Robert Smith’s A Compleat System of Opticks (1738), which detailed the methods for building telescopes, after reading Smith’s Harmonics, or the Philosophy of Musical Sounds (1749).

He also read William Emerson’s The Elements of Trigonometry (1749), The Elements of Optics (1768), and The Ideas of Mechanics (1754), as well as James Ferguson’s Astronomy explained upon Sir Isaac Newton’s ideas and made easy to people who have not studied mathematics (1756).

After learning from a local mirror manufacturer, Herschel began constructing his own reflecting telescopes after acquiring the necessary equipment and skills. He would polish and grind the principal mirrors made of speculum metal for as long as sixteen hours every day. He was dependent on other family members for help, especially his brother Alexander, a competent mechanical craftsman, and his sister Caroline.

He “began to look at the planets and the stars” in May 1773, and on March 1, 1774, he recorded his views of the Great Orion Nebula (M42) and Saturn’s rings in an astronomy notebook. While the Herschels were in Walcot (which they departed on September 29, 1777), they were visited by the English Astronomer Royal Nevil Maskelyne. By 1779, Herschel was also acquainted with Sir William Watson, who extended an invitation for him to become a member of the Bath Philosophical Society. Herschel started participating actively and would significantly broaden his network of connections through Watson. Herschel was chosen as an international member of the American Philosophical Society in Philadelphia a few years later, in 1785.

Double stars

Early on in his observations, Herschel concentrated on looking for visually close-together star pairings. At that time, astronomers anticipated that variations in the apparent separation and relative position of these stars over time would offer proof of the star’s proper motion as well as their distance from Earth through parallax fluctuations in their separation. Galileo Galilei was the one who initially proposed the latter approach.

Herschel started a systematic search for such stars among “every star in the Heavens” in October 1779, from the back garden of his home on New King Street, Bath, using a 6.2-inch aperture (160 mm), 7-foot-focal-length (2.1 m) (f/13) Newtonian telescope “with the most capital speculum” of his own manufacture. New discoveries were listed through 1792. Unexpectedly, he quickly made many additional discoveries of binary and multiple stars. He meticulously measured each star’s relative location and assembled the results into two catalogues, which he submitted to the Royal Society in London in 1782 (269 double or multiple systems) and 1784 (434 systems). 1821 saw the publication of a third list of discoveries made after 1783 (145 systems).

Herschel could have been inspired by the 1767 and 1783 publications on double star distribution and “dark stars” by the Rev. John Michell of Thornhill [34]. Herschel purchased a ten-foot-long, thirty-inch reflecting telescope from Michell’s estate following his death in 1793.

When Herschel remeasured some of the systems in 1797, he found that the shifts in their relative locations were not due to the parallax brought on by the Earth’s orbit. The hypothesis that the two stars were “binary sidereal systems” orbiting under mutual gravitational attraction was not announced until 1802 (in Catalogue of 500 New Nebulae, nebulous Stars, planetary Nebulae, and Clusters of Stars; with Remarks on the Construction of the Heavens). This hypothesis was subsequently 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.

Almost all of the verified double or multiple-star systems that Herschel found were physical rather than optical couples, totaling over 800. His theoretical and empirical contributions laid the groundwork for contemporary binary star astronomy; Friedrich Wilhelm Struve, James South, and John Herschel did not publish additional catalogs that expanded on his findings until after 1820.

Ultimately, Herschel found more than 800 double or multiple-star systems that have been confirmed, nearly all of which were physical pairings as opposed to optical ones. The basis for contemporary binary star astronomy was laid by his theoretical and observational work; New catalogs supplementing his findings were not released until around 1820 by Friedrich Wilhelm Struve, James South, and John Herschel.

Uranus

While looking for double stars in March 1781, Herschel saw what seemed to be a disk-shaped object. At first, Herschel thought he may be able to resolve it as a comet or as a star disc. He informed Nevil Maskelyne, the Royal Astronomer, about the sighting. After he made a great deal more observations of it, Russian academician Anders Lexell calculated the orbit and concluded that it was most likely planetary.

Herschel concurred and concluded that it had to be a planet outside of Saturn’s orbit. In honor of King George III, he dubbed the newly discovered planet the “Georgian star” (Georgium sidus); but, the moniker did not catch on. Until the name “Uranus” was widely used, the planet was known as “Herschel” in France, where mention of the British king had to be avoided at all costs. Herschel received the Copley Medal and was made a Fellow of the Royal Society in the same year. Not to be confused with the Astronomer Royal, he was named “The King’s Astronomer” in 1782.

Herschel relocated to Datchet (then in Buckinghamshire, now in Berkshire) on August 1, 1782, with his sister Caroline following. There he carried on with his career as an astronomer and telescope builder. He successfully sold more than sixty finished reflectors to astronomers in Britain and Continental Europe, earning him a reputation as a leading manufacturer in the world.

Surveys of the Deep Sky

From 1782 to 1802, and especially from 1783 to 1790, Herschel used two 20-foot-focal-length (610 cm), 12-and 18.7-inch-aperture (30 and 47 cm) telescopes (together with his preferred 6-inch-aperture instrument) to undertake systematic surveys in search of “deep-sky” or non-stellar objects. After removing duplicates and “lost” records, Herschel found more than 2,400 objects that he classified as nebulae. (Up until Edwin Hubble’s confirmation of galaxies as extragalactic systems in 1924, the word “nebula” was used to refer to any optically hazy celestial object, including galaxies outside of the Milky Way.

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 mentioned Catalogue of 500 New Nebulae… (1802) are the three catalogues that Herschel published his discoveries in.

Eight “classes” were used by him to organize his findings: (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 star clusters. Herschel published the General Catalogue of Nebulae and Clusters in 1864, adding to his own findings with those of his son John Herschel (1754 items) and Caroline Herschel (11 objects).

Later, John Dreyer updated this list, added findings from several other 19th-century astronomers, and it was published in 1888 as the 7,840 deep-sky objects that make up the New General Catalogue, or NGC. For these celestial markers, the NGC numbering is still the most often used identification system.

NGC 12, NGC 13, NGC 14, NGC 16, NGC 23, NGC 24, NGC 1357, and NGC 7457 are among the discoveries made by Herschel that were eventually included in the New General Catalogue.

Collaborates with Caroline Herschel, his sister

When their father passed away, William proposed that Caroline come live with him in Bath, England. Caroline’s brother had initially exposed her to astronomy in 1772.

To optimize the quantity of light caught, Caroline devoted several hours to cleaning the mirrors of high-end telescopes. She also made copies of other literature and astronomy catalogs for William. Caroline became William’s regular helper after he accepted George III’s offer to serve as King’s Astronomer.

William received a new 20-foot telescope in October 1783. William was trying to watch at this period and document all he saw. Before he could film anything, he had to dash inside and allow his eyes to acclimate to the artificial light; once inside, he would have to wait for his eyes to adjust to the darkness before he could once more observe. Caroline sat at a desk beside an open window and became his recorder. William would point out what he saw, and she would record it in her notes along with any details he needed from a reference book.

Caroline started making her own discoveries in astronomy, especially about comets. William constructed her a little Newtonian reflector telescope in 1783, complete with a handle for vertical sky sweeping. She independently discovered M110 (NGC 205), the Andromeda Galaxy’s second partner, between 1783 and 1787. From 1786 to 1797, she either found or witnessed eight comets. At her brother’s suggestion, she revised and rectified Flamsteed’s work that detailed the positions of stars. She also discovered fourteen new nebulae. Comet Encke was also rediscovered by her in 1795.

The eight comets discovered by Caroline Herschel were published between August 28, 1782, and February 5, 1787. The Philosophical Transactions of the Royal Society published five of her comets. William was even called to Windsor Castle to see the royal family Caroline’s comet. William personally noted this occurrence, calling it “My Sister’s Comet.” When her second comet was discovered, she wrote to the Astronomer Royal. When her third and fourth comets were discovered, she wrote to Joseph Banks.

The star catalogue derived from Mr. Flamsteed’s observations provided an index to almost 560 newly unrecorded stars. For her effort, Caroline Herschel received recognition in 1828 from the Royal Astronomical Society.

William Herschel’s aide, Caroline, also persisted in her role, frequently taking notes while he gazed through the telescope. George III gave Elizabeth a yearly stipend of £50 for her job as William’s helper. She became the first woman to be honored with a government job in England after her appointment. She became the first female astronomer to get compensation as a result.

Due to the wet weather, William and Caroline relocated to Clay Hall in Old Windsor in June 1785. The Herschels relocated to a new home on Windsor Road in Slough on April 3, 1786. Herschel remained living in this house, which became known as Observatory House, for the remainder of his life. In 1963 it was dismantled.

The brother-sister relationship was quite tense after William Herschel’s marriage in 1788. It has been said about Caroline that she was a resentful, envious, and spiteful lady who idolized her brother and felt her sister-in-law had invaded her personal space. Caroline lost much of her prestige and her management and social obligations in the home when Mary moved in. Caroline’s sentiments during this time are not fully known because she burned her journals between 1788 and 1798.

Caroline soon moved into a separate apartment, although she kept up her job as her brother’s helper, according to her memoir. She would frequently go back to watch after their house when her brother and his family were gone. Later in life, Caroline wrote loving letters to Lady Herschel.

In 1822, Caroline carried on with her astronomical research following William’s passing. She built nebulae catalogs and attempted to cross-check and validate his results. She organized 2,500 nebulae and star clusters into zones with comparable polar distances at the end of her life. She took this action to enable her nephew John to thoroughly reevaluate them. This catalog was eventually expanded upon and dubbed the New General Catalogue. She received the Royal Astronomical Society’s Gold Medal in 1828 in recognition of her contributions.

Herschel’s Observatories

The most popular kind of telescope at the time was the refracting telescope, which used a convex glass lens to refract light through a tube. Chromatic aberration, a distortion of an image caused by the inability of light with various component wavelengths to converge, affected this design. By combining two different lenses, optician John Dollond (1706–1761) attempted to compensate for this distortion, but it remained challenging to get acceptable resolution for far-off light sources.

When Isaac Newton created reflector telescopes in 1668, a single concave mirror was utilized in place of a convex lens. Chromatic aberration is so avoided. More light was collected by the concave mirror than by the lens, and it was reflected onto a flat mirror at the telescope’s end for viewing. Compared to a convex lens, a smaller mirror could offer higher magnification and a wider field of view. The diameter of Newton’s initial mirror was 1.3 inches; these mirrors were rarely larger than 3 inches.

Herschel discarded the tiny diagonal mirror of a conventional Newtonian reflector from his design due to the low reflectivity of speculum metal mirrors, and he slanted his primary mirror to observe the created image directly. The term “Herschelian telescope” refers to this “front view” form.

It was quite challenging to create larger, symmetrical mirrors. A picture that is blurry would arise from any imperfection. Herschel decided to construct his own mirrors since no one else was producing them in the size and magnification he wanted. This was no easy task. Caroline, his sister, and other family members helped him. According to Caroline Herschel, a mirror with a 30-foot focal length was being poured:

A day was set apart for casting, and the metal was in the furnace, but unfortunately it began to leak at the moment when ready for pouring, and both my brothers and the caster with his men were obliged to run out at opposite doors, for the stone flooring (which ought to have been taken up) flew about in all directions, as high as the ceiling. My poor brother fell, exhausted with heat and exertion, on a heap of brickbats. Before the second casting was attempted, everything which could ensure success had been attended to, and a very perfect metal was found in the mould, which had cracked in the cooling.

— Caroline Herschel

More than 400 mirrors for telescopes, ranging in diameter from 6 to 48 inches, are said to have been cast, honed, and polished by Herschel. Herschel and his helpers constructed and marketed at least sixty fully functional telescopes in a range of sizes. Herschel had another source of revenue from commissions for the creation and sale of telescopes and mirrors. A telescope was purportedly purchased for £3,150 by the King of Spain.

Mirror grinding and polishing was a crucial aspect in building and maintaining telescopes. This process has to be performed each time the mirrors are corroded or warped while being used. Using a mirror was the only method to determine its correctness.

40-foot telescope

Herschel’s most renowned and biggest telescope was a reflecting telescope with a focal length of 40 feet (12 meters) with a main mirror of 491⁄2 inches (1.26 meters). At the time, the biggest scientific equipment ever constructed was a 40-foot telescope. The achievement of “human perseverance and zeal for the sublimest science” was praised.

Herschel asked King George in 1785 for financial assistance to pay for the construction of the 40-foot telescope. He was paid £4,000. The creation of the telescope would not have been possible without royal support. As it was, it exceeded the budget and took five years.

A jumble of “labourers and workmen, smiths and carpenters” took up residence at the Slough mansion of Herschel. An iron tube for a 40-foot telescope was required. There was enough room within the tube to stroll. A mixture of copper and tin known as speculum metal was used to pour mirror blanks. They weighted one thousand pounds (450 kg) and measured about four feet (1.2 m) in circumference. A second, thicker disk was created with a larger copper content after the original one was distorted from its weight. The mirrors required a laborious hand-polishing procedure. To make sure the telescope’s mirror was correctly shaped, it was inserted and taken out several times.

A mirror that became distorted or tarnished needed to be taken out, polished again, and put back into the device. The telescope was supported by a massive rotating base that allowed assistants to move it around as the sweep went on. The resultant picture may be seen by the spectator by looking down into the tube from a platform located at the top of the tube.

Shortly after this device was put into use in 1789, Herschel found Mimas, a new moon of Saturn with a diameter of just 250 miles (400 km). Within the first month of observation, a second moon, Enceladus, was discovered.

Despite its large size, the 40-foot (12-meter) telescope was incredibly heavy and did not yield particularly good images. Herschel had pushed the boundaries of what was conceivable at the time with his technical advancements. It wasn’t until the Victorians invented methods for precisely crafting huge, fine mirrors that the 40-foot was surpassed. William Herschel felt let down by it. Herschel used a smaller 18.5-inch (47 cm), 20-foot-focal-length (6.1 m) reflector for the majority of his observations. Still, the 40-foot grabbed the attention from the general population. It captivated foreign visitors and French nobles, and it served as an inspiration to poets and scientists such as Erasmus Darwin and William Blake. George the King was happy.

Herschel’s discovery that great angular resolution may be obtained through empty telescope apertures served as the cornerstone for interferometric imaging in astronomy, namely for aperture masking interferometry and hypertelescopes.

Restoration of the 20-foot observatory

2012 saw the construction of a 20-foot telescope duplicate by the BBC television show Stargazing Live, utilizing contemporary materials together with Herschel’s original blueprints. It should not be regarded as an exact duplicate, but rather as a near-contemporary approximation. The tube is a sewage pipe, the frame is made of metal scaffolding, and the mirror is a contemporary glass mirror. The telescope is located on the University of Derby’s campus for art, design, and technology. It was featured on the show in January 2013 and will be utilized for educational reasons.

Existence on other heavenly bodies

Herschel likened the Moon to the English countryside and was certain that he had discovered abundant indications of life there. Like most of his contemporaries, he did not hold back when he theorized that life existed on the other planets, with a particular focus on Mars. When Herschel lived, most religious philosophers spoke about the special qualities of Earth, while scientists tended to believe in other civilized worlds. Herschel even ventured to hypothesize that there may be life within the Sun.

Wheat yields, climate, and sunspots

Herschel investigated the relationship between climate, solar cycle, and changes in the sun. Throughout the course of 40 years (1779–1818), Herschel kept a close eye on sunspot fluctuations in size, shape, and quantity. The majority of his observations were made during the Dalton Minimum, a time of low solar activity when there weren’t as many sunspots. This was among the factors that prevented Herschel from determining the typical 11-year cycle of solar activity. Herschel contrasted his findings with the wheat price series that Adam Smith reported in The Wealth of Nations.

Herschel presented his research to the Royal Society in 1801, revealing a correlation between the price of wheat and five extended intervals with few sunspots. Although some of his peers mocked Herschel’s research, it did spark other efforts to discover a link. William Stanley Jevons postulated the 11-year cycle later in the 1800s, building on Herschel’s fundamental theory that recurrent economic booms and busts are caused by a link between lower yields and a low number of sunspots.

Herschel is still credited with conjecturing that sunspots and local climate are related, based on his use of wheat market prices as a stand-in. One research claims that the historical wheat market in England over the 10 solar cycles between 1600 and 1700 is a direct result of solar activity. Some scientists question the relevance of the association, and the evaluation is contentious.

Infrared Radiation in Sunlight was Discovered

Herschel observed that various colored filters appeared to produce varied quantities of heat in the early 1800s as he was experimenting with different filters to let sunlight through. He made the decision to use a prism to collect data on the various hues of light using a thermometer, and in the process, he measured light that was somewhat redder than visible light. He sensed a temperature that was one degree warmer than red light. Herschel concluded after doing more experiments that there had to be an unseen kind of light that existed outside of the visible spectrum. These findings were published by him in April 1800.

Biological

With the use of a microscope, Herschel was able to prove that coral was not a plant, as many people at the time had thought, as it lacked the plant-specific cell walls. Indeed, it is a marine invertebrate, an animal.

Death and family

William Herschel wed Mary Pitt (née Baldwin), a widow, at St. Laurence’s Church, Upton in Slough on May 8, 1788. On March 7, 1792, John, their only child, was born at Observatory House. William’s son’s and his grandchildren’s upbringing was greatly influenced by his personal history and his ascent to prominence in science. In 1788, he was chosen by the American Academy of Arts and Sciences to be a Foreign Honorary Member. William received the honorary title “Sir” and the title “Knight of the Royal Guelphic Order” from the Prince Regent in 1816, although this was not the same as an official British knighthood.

In 1820, he participated in the founding of the Astronomical Society of London, which became the Royal Astronomical Society in 1831 after obtaining a royal charter. He was chosen to join the Royal Swedish Academy of Sciences as a foreign member in 1813.

After a protracted illness, Herschel passed away at Observatory House, Windsor Road, Slough, on August 25, 1822. Nearby St Laurence’s Church, Upton, Slough, is where he was laid to rest. The epitaph of Herschel is

Coelorum perrupit claustra:
(He overcame the sky’s boundaries)

His death greatly devastated Caroline, and shortly after his funeral, she made the regrettable decision to return to Hanover. She had spent fifty years living in England. Her interests were far more aligned with those of her surviving Hanoverian nephew, John Herschel, the astronomer. She kept working on classifying and organizing nebulae, producing the foundation for the New General Catalogue in the process. On January 9, 1848, she passed away.

Reminiscent

For the most of his life, William Herschel resided in Slough, Buckinghamshire, and finally Berkshire. He was buried behind the church tower of St. Laurence’s Church at Upton-cum-Chalvey, close to Slough, after passing away in the town.

Slough pays particular tribute to Herschel and his discoveries, with many memorials dedicated to him. In the heart of Slough, a new bus station was constructed in 2011; its architecture was influenced by William Herschel’s infrared experiment.

John Keats’s poem “On First Looking into Chapman’s Homer” makes reference to Herschel’s discovery of Uranus with the line, “Then felt I like some watcher of the skies/ When a new planet swims into his ken.” According to Holmes, Keats “picks out the finding of Uranus, thirty-five years before, as one of the defining moments of the age.”

The Herschel Museum of Astronomy is located in his Bath, Somerset, home at 19 New King Street, where he built many telescopes and made his first observations of Uranus.

In Westminster Abbey, there is a monument next to the choir screen.

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