Brilliant Lights

The comets of Caroline Herschel

By TANYA KLOWDEN

Restoration Conversations, Spring/Summer 2024, Issue 5

C/2020 F3 is the official designation of the brightest comet in the northern hemisphere since Comet Hale-Bopp in 1997. Known more familiarly as NEOWISE, this long period comet was discovered during the pandemic on March 27, 2020. Throughout the month of July that year, it was bright enough to be visible to the naked eye and was widely photographed by professional and amateur observers. Scientist and author Tanya Klowden was one of those attempting to photograph NEOWISE on a trip to Joshua Tree National Park in California. Here, she recounts how all the excitement over the pandemic’s own comet kept her thinking about Caroline Herschel, an astronomer known for her comet discoveries as much as for being, like many early female astronomers, her brother’s exceptionally skilled assistant. 

Stargazing from the garden of the Herschel Museum of Astronomy, ph. Bath Astronomers

Caroline Herschel (1750–1848) was never expected to amount to much of anything. With a face scarred by smallpox and standing only 4 feet and 3 inches tall, her marriage prospects were poor, her mother forbade her to learn the skills she would need to work as a governess, and so instead she was trained to carry out domestic labor in her family home, a role she would hold through her childhood and teen years, and again return to late in life, as her family dismissed her considerable accomplishments.

In between the years of forced domesticity, Caroline Herschel demonstrated a multi-faceted extraordinariness. Though she was born into a family of musicians, she was not offered the same opportunities for musical training as her brothers, the eldest two moving from their native Germany to England (specifically to Bath) to work as conductors and composers in their own right. Mercifully, following her father’s death, her brother William sent for her to join him in England to keep his own household instead of their mother’s. She did not speak the language and was intimidated by the customs and ways of the English people initially, but her brother had ideas far beyond housework. He began training her to sing and she proved every bit as musically adept as her siblings. In short order, she became the solo soprano in his oratorios, and he grew busy managing her burgeoning singing career. She was offered a permanent position as a soloist in Birmingham following her performances of the soprano solos of Handel’s ‘Messiah’, but she refused to be conducted by any musician other than her brother.

Today we might still speak of noted eighteenth-century soprano Caroline Herschel, but her brother’s conducting diminished precipitously when he developed a fascination with astronomy. As a musician with an interest in natural philosophy, William began reading Robert Smith’s treatises, first on harmonics, and then on optics. The latter book described the construction of the telescope and William quickly fell down that rabbit hole, soon trading his time at the harpsichord to grind mirrors and lenses and build his own telescopes. Caroline found herself unable to continue her music practice as her brother at all hours asked for her assistance in the matter of building telescopes and then, naturally, recording the observations made through these same devices.

A portrait of Caroline Herschel with an illustration of planets in the solar system

© The Herschel Museum of Astronomy Bath Preservation Trust

Recording astronomical observations is challenging work, requiring speed, accuracy and clarity in dark of night to leave a record that could at all be deciphered the next morning. Caroline called this “minding the heavens”. These were her mornings as her brother abandoned music to spend his time studying and cataloging double stars and discovering Uranus along the way. (I am inserting a pause here so that you may snicker. There. That’s out of the way.) He actually tried to name it Georgium Sidus but that’s not nearly so funny. In fact, William received a royal appointment as a court astronomer for discovering Uranus. While William studied objects of particular interest, he assigned Caroline the task of methodically sweeping the night sky in search of anything unusual. It was while engaged in this somewhat tedious task that Caroline made her first and second significant discoveries within a single night. The first was a nebula which was not recorded in the Messier catalog (itself a list of objects observed by French astronomer Charles Messier that were, to his frustration, definitely not comets) and the second an ellipse galaxy in close proximity to the Andromeda galaxy. Messier had actually observed the galaxy (M110) about a decade before but had not included it in his catalog, so Caroline is still credited with the independent discovery M110.

As William continued to enlist Caroline in the work of recording his astronomical observations, he (or probably, they) built a telescope specifically for Caroline to use to search for comets. Comet-fever was sweeping astronomical circles and broader society in the eighteenth century in a very similar fashion to the pandemic’s NEOWISE-borne craze. Caroline discovered no less than eight comets over an eleven-year span and independent of the clerical work she did for her brother. She was for a long while regarded as the first woman to discover a comet. While astronomer Maria Kirch had discovered a comet over eighty years before Caroline, her husband published it with his own work and despite noting that she found it while he lay sleeping, he was given the credit for the discovery for many years.

Caroline’s first comet, Comet C/1786 P1 was a hyperbolic comet. It only ever passed through our solar system once. Immediately upon recording its location in the sky in detail, Caroline wrote directly to two prominent members of the Royal Astronomical Society with the news, apologizing for not going through her brother, as he was out of the country delivering a telescope. The Society’s president, secretary, and other significant London astronomers undertook the journey to Slough so that she could show the comet to them directly. William returned home to find that his diminutive and shy sister was now famous, and the royal family summoned him to Windsor Castle to show them his sister’s comet.

Sculpture in the Herschel Museum of Astronomy garden © The Herschel Museum of Astronomy, Bath Preservation Trust

Following the discovery and her brother’s devoting less time studying astronomy and more to courting and subsequently marrying a neighboring widow, Caroline boldly asked her brother to petition the King for a salary in her own right. Officially, the salary was granted by Queen Charlotte, as Caroline was ‘the ladies’ comet hunter’. It was both the first independent income that Caroline had ever earned in her life and the first time a woman had been paid as an astronomer. 

Caroline’s second comet, Comet 35P/Herschel-Rigollet, was determined to be periodic in 1939 when it was observed again by French astronomer Roger Rigollet, and thus bears both their names. It has a 155-year period, which means it will visit the Earth again in 2092. Comets three, four, five, and six were also hyperbolic. Comet seven was observed by Messier about a decade before Caroline spotted it, and some years later, German astronomer Johann Encke was able to determine it was only the second period comet ever discovered (Halley’s comet being the first). With his prediction that it would appear again at the end of May 1822 confirmed in early June of the same year, the comet was named Comet 2P/Encke. Comet Encke has an extremely short period of 3.3 years and was last visible in 2020 in the southern hemisphere. Northern hemisphere comet-chasers would have seen it in 2023, as Caroline Herschel did.

Caroline’s final comet discovery, in 1797, was also hyperbolic, but it passed extremely close to the Earth and presented a spectacular view to the naked eye at its closest. Caroline was so eager to share the information on this discovery with the Royal Astronomer, Nevil Maskelyne, that rather than trust sending the news by post, she slept for one hour, then saddled her horse and rode for six straight hours through the night to present the information to him in person. I imagine this was very much like Paul Revere’s ride except about astronomy, and also side-saddle. Her excitement over the comet put her in the typical Austen-heroine position of having to stay at the Royal Astronomer’s home for several days to recover from her wild journey.

After her brother’s death, Caroline returned to Germany and, though she continued to make some astronomical observations, she was largely relegated back to being the household servant. She spent time reorganizing and rewriting the nebula catalog she had collaborated on with her brother and shared many of his observations with her nephew, who stayed in England and carried what was now the Herschel tradition of astronomy forward. In 1828, the Royal Astronomical Society presented her with the Gold Medal for the catalog and her celestial discoveries. She was the first woman to be granted this prestigious award. The second woman to receive this honor (for her work on galactic rotations), Vera Rubin, was awarded her medal in 1996. Caroline also was awarded an honorary (not a full) membership in the Royal Astronomical Society in 1835. She and Mary Somerville became the first women to be awarded this honor. While she continued to receive accolades in her later years, she had stopped her observations some four years prior to receiving the Royal Astronomical Society medal.

She died twenty years after drawing her astronomical studies to a close, at the age of 97. It is difficult to gaze up at the fleeting spectacle of a comet whizzing by and not think about Caroline. There are billions of dusty snowballs rocketing through our solar system unnoticed in the darkness and cold of space. It is only as one or another comes streaking toward the sun that the powerful illumination warms it and brings its distinctive glow, a brilliant point of light with a glorious train trailing behind it. It is in that moment that we are transfixed by the spectacle, by the splendor of it, and as we gaze, the comet speeds past, into darkness, into obscurity once again.

Like many of the great women of science Caroline, too, faded into obscurity. Unremarkable in their seeming ordinariness, they all needed the light to shine. In the moment of discovery, we are astounded, amazed by their brilliance, and for a season no one can look away. Then, a heartbeat, two, three, and too many are forgotten, retreating into darkness again. 

We do not know which of the uncountable billions in the darkness will one day shine, only that there are always more waiting to be discovered, surprising us, enchanting us with their dazzling light. Nor do we know which will vanish from our view, too fleetingly faded, too quickly gone. Still, for each woman in obscurity, each comet that has not yet had its moment to shine, we can do as Caroline did. We can record the brilliance of those that shine before us, share their stories, name them so they will not be forgotten when they have left us. When we recognize they are extraordinary they show us how to shine. And, just as with NEOWISE, we all need that remarkable light in the world. It is what guides us through the darkness that otherwise would engulf us. 

Tanya Klowden is a scientist, art historian, designer, and parent. She holds graduate degrees in Physics and Art History and has written topics ranging from technology and climate change to the roles of women in the sciences and arts. As she writes, she seeks to amplify the voices that have been diminished or marginalized through history.