William Herschel Biography

Frederick William Herschel, [1] KH, FRS (German: Friedrich Wilhelm Herschel ; 15 November 1738 – 25 August 1822) was a British astronomer and composer of German and Czech-Jewish origin, and brother of fellow astronomer Caroline Herschel, with whom he worked. Born in the Electorate of Hanover, Herschel followed his father into the Military Band of Hanover, before migrating to Great Britain in 1757 at the age of nineteen.

Herschel constructed his first large telescope in 1774, after which he spent nine years carrying out sky surveys to investigate double stars. The resolving power of the Herschel telescopes revealed that the nebulae in the Messier catalogue were clusters of stars. Herschel published catalogues of nebulae in 1802 (2,500 objects) and in 1820 (5,000 objects). In the course of an observation on 13 March 1781, he realized that one celestial body he had observed was not a star, but a planet, 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 as a Fellow of the Royal Society and grants were provided for the construction of new telescopes.

Herschel pioneered the use of astronomical spectrophotometry as a diagnostic tool, using prisms and temperature measuring equipment to measure the wavelength distribution of stellar spectra. Other work included an improved determination of the rotation period of Mars, the discovery that the Martian polar caps vary seasonally, the discovery of Titania and Oberon (moons of Uranus) and Enceladus and Mimas (moons of Saturn). In addition, Herschel discovered infrared radiation. Herschel was made a Knight of the Royal Guelphic Order in 1816. He was the first President of the Royal Astronomical Society when it was founded in 1820. He died in August 1822, and his work was continued by his only son, John Herschel.

Sir William Herschel - © Gemälde von Lemuel Francis Abbott, 1785, National Portrait Gallery, London

Other astronomical work

In 1787, Herschel discovered two satellites of Uranus, Oberon, and Titania.

Herschel worked on creating an extensive catalog of nebulae and double stars, the first of these being published in 1782. He orignally tracked double stars in the hope that they would provide a clue to stellar distances through a comparison of the the stellar luminosities of each pair, provided that their closeness was simply a matter of chance, one of the stars being in reality much more distant than the other. In 1803, however, he announced his conclusion that most double stars are not mere optical doubles as had been supposed previously, but are true binary stars held together by mutual attraction, thus providing the first proof that Newton’s laws of gravitation apply outside the solar system. Herschel also studied variable stars, which fluctuate in luminosity.

In one of the most remarkable and far-reaching discoveries of the nineteenth century, Herschel in 1800 reported the discovery of infrared radiation by passing sunlight through a prism and holding a thermometer just beyond the red end of the visible spectrum. This thermometer was meant to be a “control” to measure the ambient air temperature in the room. He was shocked when it showed a higher temperature than the visible spectrum. Further experimentation led to Herschel’s conclusion that there must be an invisible form of light beyond the visible spectrum, and that this form of radiation transmits heat.

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 (toward the constellation Hercules). He also studied the structure of the Milky Way and concluded that it was in the shape of a disk.

He also coined 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 of the same year), 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.

Despite his numerous important scientific discoveries, Herschel was not averse to wild speculation. In particular, he believed every planet was inhabited, even the Sun: he believed that the Sun had a cool, solid surface protected from its hot atmosphere by an opaque layer of cloud, and that a race of beings adapted to their strange environment lived there that had enormous heads.

Herschel made a few other miscalculations in in his career. He tried to estimate stellar distances based on the assumption that stars are roughly the same size and type as the sun and by comparing the luminosity of each. This assumption proved to be faulty. He also assumed that nebulae were all composed of individual stars, which would be revealed as the resolution of telescopes improved. He eventually corrected this misconception. Herschel also reported the existence of four additional satellites of Uranus that could not be confirmed by others. And he reported volcanic activity on the moon that no astronomer has seen since.

Astronomy

HerschelTelescope

Herschel’s music led him to an interest in mathematics and lenses. His interest in astronomy grew stronger after 1773 and he made the acquaintance of the English Astronomer Royal Nevil Maskelyne. He started building his own reflecting telescopes and would spend up to 16 hours a day grinding and polishing the metal primary mirrors.

Uranus

When he discovered Uranus, Herschel was not looking for a planet but doing a survey of stars; it was an accidental discovery.

It was the first discovery of a new planet since ancient times. The first five, Mercury, Venus, Mars, Jupiter and Saturn, are visible with the naked eye, and have been known since early history. Uranus was the first discovered by telescope. Actually, Uranus had been seen before by other observers with telescopes, but had been marked on charts as a fixed star. Herschel found it moved against the background of stars, and at first thought it was a comet. His measurements were used by the French mathematician Pierre Laplace, who worked out its orbit, and proved it was a planet.

Herschel called the new planet the ‘Georgian star’ (Georgium sidus) after King George III, which brought him favour; the name did not stick, 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. The same year, Herschel was awarded the Copley Medal and elected a Fellow of the Royal Society. In 1782, he was appointed “The King’s Astronomer”. He got a generous award from the king, which enabled him to stop work as a musician, and devote all his time to astronomy. The award was a life pension to Herschel of £200 a year, and £50 a year to Caroline. Work on the 40-foot telescope was also supported by a grant from the king. p6

Herschel’s telescopes

Herschel 40 foot

During the course of his career, he constructed more than four hundred telescopes. He was helped in this by his brother Alexander who, like Caroline, spent all his time working as Herschel’s assistant.

The largest and most famous of his telescopes was a reflecting telescope with a 48-inch-diameter (1.2 m) main mirror and a 40-foot (12 m) focal length. This was the world’s largest telescope from 1789 until it was dismantled (taken apart) 50 years later. p6 The mirror was made of a hard metal alloy of tin and copper, called ‘speculum’, which he polished by hand.

On 28 August 1789, his first night of observation using this instrument, he discovered a new moon of Saturn. A second moon followed within the first month of observation. However, the 40-foot telescope was awkward to use, and most of his observations were done with a smaller 18.5-inch (47 cm) 20-foot-focal-length (6.1 m) reflector.

He continued his work as a telescope maker, selling many of them to other astronomers. Together with his pension from the king, the money helped support him and his two siblings in their work.

Star catalogue

Herschel used to work with his sister Caroline Herschel. She recorded his observations as he made them. In 1783 he gave Caroline a telescope, and she began to make astronomical discoveries in her own right, particularly comets.

Caroline discovered eight comets, three nebulae and, at her brother’s suggestion, updated and corrected Flamsteed’s work on the position of stars. This was published as the British Catalogue of Stars. She was honoured by the Royal Astronomical Society for this work. Caroline also continued to serve as his assistant.

Binary stars

Herschel was the first to find out that some line-of-sight apparent double stars were actually true binary star systems where the two stars revolved around each other. This was the first evidence that Newton’s laws of gravitation apply outside the Solar System. Herschel discovered 850 binary stars, and worked up the first catalogue of binary stars. His son John Herschel discovered many more, and extended the catalogue.

Solar System and Milky Way

Herschel studied the changes in star position relative to the Solar System. Changes do occur, and quite rapidly for some nearby stars. Also, the whole Solar System moves, and this was discovered by Herschel.

From studying the proper motion of stars, he was the first to realize that the solar system is moving through space. He worked out 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. This was also a really significant discovery.

Discovery of infrared radiation

On 11 February 1800, Herschel was testing filters for the sun so he could observe sun spots. When using a red filter he found there was a lot of heat produced.

Herschel discovered infrared radiation by passing sunlight through a prism and holding a thermometer just beyond the red end of the visible spectrum. This thermometer was meant to be a control to measure the ambient air temperature in the room. He was shocked when it showed a higher temperature than the visible spectrum. Further experimentation led to Herschel’s conclusion that there must be an invisible form of light beyond the visible spectrum.

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Herschel

Biography of William Herschel, a German astronomer and musician, discoverer of the planet Uranus and numerous other celestial objects, brother of astronomer Caroline Herschel and father of also astronomer John Herschel.

In the cover you can see a portrait of William Herschel made by Lemuel Francis Abbottv in 1785. Credit: wikipedia

Childhood and education of William Herschel

William Herschel, was born in Hanover, Germany on November 15, 1738.

Hanover. Biography of William Herschel

Hanover city capital of Lower Saxony Land, northwestern Germany. Credit: web “britannica.com/place/Hannover-Germany”

Herschel’s parents were Isaak Herschel,a military musician, and Anna Ilse Moritzen.

Influenced by his parents, Friedrich studied music and became a competent oboe player, joining his father and his brother Jacob in the band of the Guards Infantry Regiment.

In 1757 William Herschel participated in the Battle of Hastenbeck, between France and Hanover during the Seven Years’ War.

Hastenbeck. Biography of William Herschel

The Battle of Hastenbeck on July 26, 1757. Credit: Wikipedia, Author: French painter Louis Edouard Rioult.

Herschel decided to go to England

The more than 5,000 deaths that he witnessed, made a deep impression on him, and led him to move away from his native country and settle with his brother Jacob in England.

After two years, Jacob decided to return to Hanover but William preferred to stay.

The young Herschel deepened his musical studies in England: he became first a teacher and then an organist in Halifax .

Halifax

The city of Halifax In 1834. Credit: Wikipedia. Author Charles Knight.

The following year, Herschel was appointed conductor in Bath.

Since he was single, he decided to ask his sister Caroline Herschel came to live with him in Bath.

In 1772, his sister Caroline Herschel came to live with him in Bath.

It was then that, thanks to Caroline’s influence, the episode that would change William’s life occurred.

Herschel’s Beginnings in Astronomy

On May 10, 1773, Herschel bought a book (Ferguson’s “Astronomy”) and fell forever in love with the science of the heavens.

A man hungry for knowledge and gifted with great manual skills, Herschel began from the beginning to calculate, design and build his own telescopes.

Less than a year after purchasing Ferguson’s book, hungry for knowledge and gifted with great manual skills, Herschel was already calculating and polishing the most perfect and powerful mirrors in the world.

Because he quickly understood that the future depended on reflecting telescopes, he started designing and building his own telescopes.

He built a telescope that had a lens 40 cm in diameter and 12.20 meters in length, of his own manufacture (he was very skilled at this).

His first great discoveries were made with the help of his first telescope, which he used until the end of his life.

While building custom telescopes, very abundant in those years of the “Enlightenment”, he observed the skies helped by his sister Caroline who wrote down all the details that William saw.

Herschel’s Astronomical Discoveries

As early as February 1774, they had already observed and analyzed in detail the Orion Nebula, discovered earlier in 1610.

Nebula Orion. Biography of William Herschel

Orion Nebula M42 .Orion Nebula Credit: Wikipedia

On March 13, 1781, Herschel observed an unrecorded object that at first glance looked like a comet: studying it carefully he soon managed to determine that it was actually a new planet.

It glowed yellow and moved slowly. Observing it night after night, Herschel concluded that he had discovered the seventh planet in the Solar System.

Herschel tilted the mirror of his telescope slightly so that it did not block the incident rays. Hershell had discovered the seventh planet of the solar system.

Later, in 1787, Herschel discovered Titania and Oberon, two moons of Uranus.

How the name of the seventh planet was chosen

Herschel asked other astronomers to confirm his diagnosis, and they all agreed with him: there was a new planet located twice the distance from Saturn.

Herschel baptized the planet with the curious name “Planet George“, in a strange tribute to King George III of England who had just lost all his possessions in North America due to American independence in 1776.

The “Planet Jorge” continued to be called that way until well into the 19th century, despite opposition from some astronomers who insisted that the mythological tradition should be continued.

According to them, as the names of the adjoining planets were Mars, Jupiter and Saturn, to continue with the genealogical sequence: grandson, father, grandfather.

Urano

Uranus how Uranus would appear in visible light. It’s a courtesy of NASA/JPL-Caltech

The French astronomer Lalande proposed, for his part, to baptize the planet as “Herschel“. But this idea was not accepted and the name of Uranus prevailed.

However, until 1850 the British “Nautical Almanac” continued to cite the planet “Jorge” in its astronomical ephemeris.

Honors Received by the Herschel Brothers

King George. Biography of William Herschel

Portrait in oils of a King George III in coronotion robes. Credit: Wikipedia. Author: Allan Ramsay

King George III awarded Herschel for his discovery of Uranus by naming him a member of the Royal Society of Sciences and a Royal Astronomer of the Court.

Thanks to the salary that this appointment provided him, the astronomer was able to definitively abandon music as a way of life and dedicate himself exclusively to his science.

He made more and better observations, always assisted by his sister Caroline, who also began to receive an official salary, and began to build increasingly powerful and evolved instruments.

Other astronomical investigations of Herschel

In 1782, a friend he had met at the Royal Society, William Watson, presented him with a Messier Catalog, which stimulated Herschel’s interest in nebulae and clusters, collectively called “deep space objects”.

In August 1782, Herschel began investigating the objects described in Messier’s book, with his telescopes, more powerful than those that Charles Messier, author of the Catalog, ever possessed.

He realized that Messier’s book contained only a tiny fraction of the deep space objects in reality.

On October 23, 1783, with the help of Caroline and using his 157x refractor, he began a systematic search of all parts of the sky visible from his observatory.

Five days later he made his first discovery: NGC 7184, a small galaxy in the constellation Aquarius of magnitude 11.2.

In a year and a half he discovered 1,000 new deep space objects, the list of which he published in his own Catalog of 1786.

The Eskimo Nebula in the constellation Gemini, was discovered by Herschel in 1797.

Eskimo nebula

NGC 2392, nicknamed the “Eskimo Nebula”, is what astronomers call a planetary nebula. Credit: web “nasa.gov/mission_pages/chandra/news/eskimo-nebula”

In a span of less than two decades, Herschel discovered 2,514 new deep-space objects, including globular clusters, nebulae and galaxies.

Milky Way

Together with his sister Caroline, he set about not only counting stars, but also drawing a complete map of the Milky Way.

The result, although very primitive, is remarkably close to what is known today.

In 1783, Herschel verified that the Sun was not still as the theory of Copernicus and Galileo supposed. By comparing the positions of different relatively “fixed” stars.

He showed that the Sun drifts toward the star Lambda Herculis, dragging Earth and the rest of its planetary entourage.

Biographie of William Herschel last years

In 1788, Herschel married the widow Mary Baldwin Pitt, who had been married to the powerful London merchant John Pitt.

Mrs. Pitt had lost her first husband two years before meeting Herschel.

In 1789, after working non-stop for two years, he completed the construction of a large telescope with an aperture of 1.20 meters, which for more than 50 years held the mark of being the largest telescope in the world.

He aimed it at the night sky for the first time on August 28 and within minutes he discovered the sixth moon of Saturn.

Three weeks later, on September 17, he detected the seventh moon of Saturn, which gives an idea of ​​the extraordinary optical quality of that huge instrument.

Saturn moons. Biography of William Herschel

Saturn, its rings and major icy moons. Credit: Wikipedia. Web “photojournal.jpl.nasa.gov/catalog/PIA03550

But the giant was difficult to operate, so Herschel continued to prefer his old, reliable 18-inch with which he had discovered thousands of galaxies in the past and with which he was able to discover “spiral nebulae”.

Hershel studied the proper motion of the stars and based on statistics of the star populations in each sector of the sky, he designed a fairly correct model of the Milky Way.

In 1792 she gave birth to the astronomer’s only son (who, in time, would follow in the footsteps of his father), John Herschel, in Slough, England.

In 1801 Herschel traveled to Paris, where he met the renowned French scientists Pierre Simon Laplace and the aging Messier.

Napoleon learned of the presence of these three reunited celebrities, he received them in his official office and spent long hours with them being interested in his discoveries.

In 1806 Napoleon imposed the Cross of the Legion of Honor on him.

William Herschel passed away on August 25, 1822 at his home in Slough, at the ripe old age of 84.

When William died, his sister Caroline left England and returned to Hanover.

Her wife, Mary, remained in the family home until her own death ten years later.

Science has honored William Herschel

In the courtyard of the Slough house a monument has been erected, located in the precise place where William mounted his enormous telescope.

An exact replica of this telescope is kept at the National Observatory of Spain, in El Retiro Park.

In the time of Carlos III, the Spanish government had bought a copy of Hershell’s telescope from him.

The transfer of this, was made by boat to the north of Spain; and, from there, on the back of a mule train.

During the French invasion in the early 19th century, French soldiers destroyed the Observatory and the telescope.

Fortunately, all the original plans had been preserved, which were used for its later reconstruction, which can be observed with admiration by the visitors of the current Observatory.

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