The Herschels were pioneers of the systematic classification and investigation of the heavens. William Herschel was one of the first ‘professional’ astronomers, and discovered infrared radiation. His sister Caroline helped him to develop the modern mathematical approach to astronomy.

These two remarkable individuals were the subjects of Dr Sue Bowler’s presentation to Keighley Astronomical Society on Thursday 25th January 2024. Dr Sue Bowler FRAS from the School of Earth and Environment at the University of Leeds, is a regular visitor to our society and that was reflected in the large number of members who attended.

Dr Bowler started her presentation with William in Germany. He was the son of a musician, was born in Hanover, in 1738. His original name was Friedrich Wilhelm Herschel.

Williams father Isaac was the head of a poor family but Isaac believed in education and enthused his children by showing them the wonders of the night sky. He also loved to discuss philosophical and mathematical subjects with his children. Isaac’s work for the Hanoverian foot guards may not have been well paid but it did mean that his children could attend a school run by the Guards.

William followed in his father’s footsteps, joining the Hanoverian Guard band to play the oboe. He did see action in the Battle of Hastenbeck in July 1757, unfortunately on the losing side against the French.

William was just 19 years of age when he left the military (without discharge papers), and moved to England to teach music in 1755. His connections to the north of England commenced five years later when he accepted a position as head of the Durham Militia Band and lived in Richmond, North Yorkshire. During these years William wrote several symphonies and through writing music it drew his attention more and more towards mathematics.

In 1766 William was just a stones throw from Keighley when he won a competition to become organist at the parish church in Halifax. However, at almost the same time he received an invitation to become the organist at the privately owned Octagon Chapel on Milsom Street in Bath. This was a much more attractive offer but William felt that he had to be fair to Halifax so he remained there for a few months, only leaving for Bath in December of 1766. Halifax made an effort to keep him with an offer of a higher salary but the attraction of Bath was too great.

In 1772, wishing to help his sister Caroline, he travelled to Hanover and brought her back to Bath with him so that she could become a trained singer. He had to agree to pay his mother enough to employ a servant before she would allow Caroline to leave. Back in Bath William gave Caroline lessons in singing, playing the harpsichord and in bookkeeping. She became his housekeeper, and soon found herself equally captivated by the night sky.

In addition to mathematics, William started to purchase astronomy books and tables. For example he purchased James Fergusons’s ‘Astronomy’ in 1773. Other books he had purchased included two of Robert Smith’s books, ‘Opticks and Harmonics’, Emerson’s ‘Trigonometry’, and Robert Simson’s ‘Euclid’.

He still earned his living as a major figure in the musical life of Bath, as a teacher, performer, composer and director. By the end of 1773 the passion for astronomy had firmly gripped him and had taken over the lives of the Herschels.

In September the same year William hired a small Gregorian telescope of the style designed by James Gregory. Its performance was not particularly good so that William decided that he would build his own telescopes. He developed and refined Isaac Newton‘s designs to avoid problems with poor glass optics. Herschel cast and polished his own mirrors, producing ever bigger and better telescopes. His previous experience in repairing and making his own musical instruments came to his aid in this matter.

In 1781, while working alone, William discovered the planet Uranus. He was unsure whether it was a comet or a planet. Most astronomers thought that it was a planet and this was confirmed by Anders Lexell who computed its orbit, finding its distance from the sun to be 16 times the distance of the earth from the sun. Pierre-Simon Laplace independently obtained a similar result from his calculation of the orbit. William originally named it ‘Georgium Sidus’ in honour of the British King.

The discovery of the new planet inspired Herschel to cease his career as a musician and teacher and concentrate solely on astronomy. King George III appointed William his private astronomer in 1782, (The position of astronomer Royal) and paid him pension of £200 a year on the condition he came to live near Windsor. Caroline and William moved to live in Slough.

His paper ‘On the Construction of the Heavens’, published in 1784, modelled the formation of our Galaxy, the Milky Way, and marked the beginnings of the Herschel’s life-long interest in the cataloguing of the Universe. Caroline diligently recorded all the observations made by William contemporaneously.

By 1789, Herschel had built a 12-metre-long reflector, the largest telescope of its day.

Caroline started performing her own ‘sweeps’ of the night sky and on 1st August 1786 she discovered her first comet, the first to be recorded as being discovered by a woman. She found seven more in the years between up to 1797, and she also discovered three nebulae. In 1787 she was granted a salary of £50 by the King to act as her brother’s assistant. The first woman to be paid as a professional astronomer.

Caroline worked hard in her own right, and in 1798 she published the ‘Index to Flamsteed’s Observations of the Fixed Stars’, a list of corrections and 560 additional stars. This was an addition to the posthumously published catalogue of John Flamsteed, who had been the first Astronomer Royal in England, in the later 17th/early 18th century.

After discovering moons around Saturn and Uranus, Herschel turned his attention from the planets to the stars. He drew up a catalogue of double stars and showed that some were orbiting pairs.

In 1800, Herschel described how the various coloured filters through which he observed the Sun allowed different levels of heat to pass. He performed a simple experiment to study the ‘heating powers of coloured rays’: he split the sunlight with a glass prism into its different constituent colours and measured the temperature of each colour. He observed an increase as he moved the thermometer from the violet to the red part of the ‘rainbow’.

Herschel also measured temperatures in the region just beyond the red colour where no light was visible and, to his surprise, recorded an even higher temperature there. He deduced the presence of invisible ‘calorific’ rays, now called ‘infrared’ radiation, and provided the reason for naming the European Space Agency’s infrared space observatory after him. During the rest of his life, Herschel produced lists of thousands of nebulae and star clusters, and he was the first to distinguish between distant clusters and dusty nebulae.

Caroline created an index to John Flamsteed’s star catalogue ‘Atlas Coelesti’ making corrections and adding 560 stars missing from the original.

In April 1820 the Council of the Astronomical Society asked William to become their first President, stating that he would not be required to give any active service. William refused but accepted in the following year becoming the Royal Astronomical Society’s first President.

After William’s death in 1822, Caroline returned to Hanover and re-organised his catalogues into one extensive book, for which she was awarded a Gold Medal by the Royal Astronomical Society, who later elected her a member in 1828.

In 1835, Caroline was one of the first two women to be accepted as a member of the Royal Astronomical Society, alongside Mary Somerville. When she died in 1848, at the age of 97, Caroline was highly regarded by the astronomical community across Europe.

Sir William Herschel discovered, in addition to the planet Uranus, many new nebulae, clusters of stars and binary stars. He was the first person to correctly describe the form of our Galaxy, the Milky Way.

An asteroid was named Lucretia in 1889 in honour of her second name. This was a fitting tribute to someone who had contributed so much yet disliked the praise directed towards her when it detracted from her brother.

Concluding the presentation Dr Bowler gave examples of the wider field of William Herschel’s studies. He examined the correlation of solar variation and solar cycle and climate. Herschel compared his observations with the series of wheat prices published by Adam Smith in publication ‘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

He 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.

William Herschel was sure that he had found ample evidence of life on the Moon and compared it to the English countryside. He did not refrain himself from theorising that the other planets were populated, with a special interest in Mars, which was in line with most of his contemporary scientists. During his time, scientists tended to believe in a plurality of civilised worlds; in contrast, most religious thinkers referred to unique properties of the Earth. Herschel went so far as to speculate that the interior of the Sun was populated.

On 25th August 1822, William. He was buried at St Laurence’s Church, Upton, Slough.
His epitaph is
‘Coelorum perrupit claustra’ He broke through the barriers of the heavens.

Caroline was deeply distressed by his death, and soon after his burial she returned to Hanover. She died on 9th January 1848.