William Herschel

William Herschel
Part of the tube is all that remains of William Herschel's 40-foot telescope. It's on display near the old Royal Observatory in Greenwich, England. [Image credit: Michael Herrick]

A professional musician named William Herschel (1738-1822) was the first person in history to discover a planet. Later, as a professional astronomer and telescope maker, Herschel studied the stars and deep space objects to try to understand “the construction of the heavens.” He was one of the fathers of modern astronomy.

Family and early life
Isaac Herschel and Anna Moritzen of Hanover – now part of Germany – had six surviving children. Isaac was a military bandsman, and his four sons became musicians. Even the younger daughter Caroline became a singer, though she's better known as an astronomer.

As a teenager William joined the band of the Hanoverian Guards, but when war broke out Isaac got him safely away to England. This caused some problems, for although William hadn't taken the military oath, his absence wasn't unregarded. It was several years later that all was resolved by an official discharge.

It was in the southern town of Bath that Herschel finally became an established musician. He was the organist for the Octagon Chapel, a concert arranger, performer, composer and teacher. His brother Alexander also came to Bath, and in 1772 they decided to rescue their sister Caroline. She was was languishing in Hanover, treated as a servant by her mother and eldest brother.

William took Caroline to Bath to train as a singer. He got his mother's support for this by offering to pay for a servant for her. Caroline had a lovely voice and became an accomplished singer.

A passion for astronomy and double stars
Astronomy had long been an interest of William's, but it grew into a passion in the 1770s. He read about optics and astronomy, and began observing. He also made his own telescopes.

One of his interests was double stars. Astronomers of the time assumed that these stars seemed to be close together because they happened to be in our line of sight. Therefore they could be the key to stellar parallax, a way of calculating distances to the stars. Over several decades Herschel published three catalogs of double stars. From his observations he concluded that, in fact, most of the doubles weren't just chance alignments, but physically connected.

Discovery and celebrity
On March 13, 1781, Herschel was observing at 19 New King Street, Bath when he found what seemed to be a comet, and reported it to the Royal Society. But it turned out to be something entirely unexpected – a previously unknown planet. Since pre-history, five planets had been seen from Earth. They're all visible to the unaided eye, and no one could be said to have discovered them.

Herschel cannily named the planet Georgium Sidus (George's Star) after George III, King of England and ruler of Hanover. In return, the King, a keen amateur astronomer, offered William the job of King's Astronomer. His only duty would be occasionally to show the night sky to the royals and their guests.

Although Herschel's discovery received international recognition, naming the planet after the English king wasn't popular abroad, especially in America and France. Eventually, the name Uranus – after the sky god and father of Saturn – was accepted.

The astronomers
The Herschels moved to the village of Datchet to be near Windsor and the royal family. With William's encouragement, Caroline also began observing.

Today nebulae, star clusters and galaxies are all deep sky objects. In 18th century telescopes they were just fuzzy blobs known as nebulae, but William got curious about them and decided to survey them. With Caroline's help, nearly 2500 northern hemisphere objects were cataloged.

Besides being William's assistant, Caroline discovered eight comets and published an index to Flamsteed's star atlas. When the king gave her a salary for her work, it made her the first professional woman astronomer in Britain.

In 1786 they moved to Slough where William spent the rest of his life. In 1788, he married Mary Pitt and they had one child, John Herschel, who became one of his era's most distinguished scientists.

The nebular survey was carried out with the 20-foot reflecting telescope William had built. When, in his seventies, William's health began to fail, he persuaded his son John to take up astronomy. They rebuilt the telescope, and many years after his father's death, John took it to South Africa to observe the southern skies and complete the nebular survey.

The Herschels built and sold telescopes, but William's most famous creation was a 40-foot telescope for which he got a grant from the King. It was a prominent local landmark, but far from aiding William's quest to understand the heavens, it was a burden. The monster was cumbersome to use and in need of constant maintenance.

Other discoveries
Herschel was a prodigious observer. Besides numerous deep sky objects, he discovered two moons of Uranus and two of Saturn. When his investigations led to the detection of infrared radiation, he was the first person to realize that there is radiation invisible to our eyes. He made one of the first attempts to model the Milky Way using scientific method. It was crude, but it did show the Galaxy as a disk.

After many years of poor health, William Herschel died on August 25, 1822 at Observatory House. He's buried in St. Laurence's Church in Upton, Slough. Part of his epitaph reads “Coelorum perrupit claustra.” (He broke through the barriers of the heavens.) He had lived for 84 years, the time it takes his planet Uranus to orbit the Sun once.

You Should Also Read:
Caroline Herschel
John Herschel
Herschel Museum of Astronomy

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