Sir William Herschel: the astronomer who discovered Uranus

The life and work of Sir William Herschel, the famous astronomer who went looking for comets and found a planet.

The astronomer Sir William Herschel. Credit: DEA PICTURE LIBRARY / Contributor

Sir William Herschel is certainly a name for anyone interested in astronomy to know: discoverer of the planet Uranus, pioneer of sidereal astronomy and designer of what was the world’s biggest reflector from 1789 to 1845.

Advertisement

William Herschel was born in Hanover (in modern-day Germany) on 15 November 1738. His was a large, poor, musical family with aspirations.

His father was a self-taught musician, who earned his living playing with a local military band; his mother a busy, illiterate, matriarch who took on sewing to make ends meet.

At home William and his brothers received an intensive musical education; at school they were the beneficiaries of reforms that ensured they, unlike their parents, received an academic education that included reading, writing, arithmetic and even French.

When Herschel was 19, his parents sent him to England, not only because opportunities for musicians were greater there than in Germany, but also to keep him safe during the Seven Years’ War (1756–63).

He got work, but found the uncertainty of life as a musician troubling. For a decade he worked as a musician while, in his spare time, educating himself in natural philosophy.

Ever the performer, William spent these years cultivating a public persona of musician-philosopher, musing over the wonders of the Universe with his wealthy employers.

In the late 1760s he got a more settled job as an organist in Bath and brought over his brother Alexander and sister Caroline to help build his musical business.

Together, for another decade, they performed concerts, taught music and began to build telescopes.

Then, on 13 March 1781, using one of his family-made scopes, William discovered a planet.

Announced as a comet at first (Herschel took a cautious approach since no one had ever discovered a planet before), news of the discovery spread quickly through the scientific community and around the world.

The Royal family wanted to see his planet (later named Uranus); astronomers wanted to see his telescopes and determine if they were as powerful as Herschel claimed.

Soon he was given a new job, as Astronomer Royal, moving to Slough to be nearer his Royal patrons and bringing his sister Caroline with him.

A replica of the telescope with which Herschel discovered Uranus, on display at the Herschel Museum of Astronomy in Bath, UK. Credit: Mike Young (https://en.wikipedia.org/wiki/William_Herschel)
A replica of the telescope with which Herschel discovered Uranus, on display at the Herschel Museum of Astronomy in Bath, UK. Credit: Mike Young (https://en.wikipedia.org/wiki/William_Herschel)

Discounted objects

Astronomers at the time concerned themselves almost exclusively with our Solar System. Their job, as they saw it, was to measure with increasing accuracy the exact movements and dimensions of the Sun and Moon, planets, asteroids and comets.

When they did venture beyond that remit, it was to identify (and so discount) any objects that could easily be mistaken for comets.

William and Caroline Herschel, in contrast, were interested in those discounted objects. Their catalogues listed thousands of deep-sky objects.

And not only did they list them, William categorised them and, in doing so, developed a theory of stellar evolution and estimate for the size and shape of the Milky Way.

Looking out beyond the Solar System, to try to resolve these point-like objects and identify and catalogue those
that weren’t single stars meant the Herschels needed big, powerful telescopes.

William had discovered the planet Uranus using his 7-foot long (2,133mm) reflector (copies of which – made and sold by him – can be found in many museums).

He also made a 10-foot, 20-foot, 30-foot and finally a 40-foot reflector.

The Herschels’ 40-foot (12,192mm) reflector, completed shortly after William got married, quickly became a symbol of British science.

It was built with Royal money – a grant for the building work and an annual pension for Caroline as co-operator – and soon drew crowds to see it in Slough.

It was marked on the first Ordnance Survey map and, combined with the draw of William and Caroline – the famous comet-hunter – attracted many visitors.

Men and women of science came, as too did aristocrats and dignitaries.

William Herschel died in Slough at his family home-turned-observatory on 25 August 1822. By then he was perhaps the most famous astronomer in Europe.

He had turned astronomers’ attentions from the internal workings of the Solar System to the stars beyond.

Through his promotion of his sister’s work, he had helped open the door to women in science.

He had changed the image of astronomy too, blending the professional’s need for large, powerful instruments
with the amateur’s curiosity and passion for exploration and discovery.

A guide to the Herschel family

Alexander Herschel (1745–1821) William’s brother was a musician who helped him build telescopes.

Caroline Herschel (1750–1848) William’s sister was his astronomical collaborator, a discoverer of comets and the first woman to publish with the Royal Society.

John Herschel (1792–1871) William’s son, is known to astronomers for completing his father’s cataloguing project for the Southern Hemisphere.

John Herschel the Younger (1837–1921) William’s grandson observed and recorded eclipses from India where he was stationed as an engineer.

Constance Herschel (1855–1939) William’s granddaughter studied at the University of Cambridge. In later life, she wrote The Herschel Chronicles, about the life and work of her grandfather and great aunt.

Advertisement

This article originally appeared in the November 2019 issue of BBC Sky at Night Magazine. Dr Emily Winterburn is author of The Quiet Revolution of Caroline Herschel: The Lost Heroine of Astronomy.