Caroline Herschel

Today is the birthday (as you may have noticed on Google’s doodle for the day) of one of the earliest women astronomers: Caroline Lucretia Herschel. Born in Hanover in 1750 she was the eighth child and fourth daughter of musician Isaac Herschel and his wife, Anna Ilse Moritzen. A bout of typhus at age 10 stunted her growth, so that she never grew past four feet three inches. Her family assumed that she would never marry and her mother felt it was best for her to train to be a house servant but her father, against the wishes of his wife, wanted Caroline to receive an education. Isaac sometimes took advantage of her Anna’s absence to teach his daugther directly or include her in her brother’s lessons. Following her father’s death, her brother William proposed that she join him in Bath, England, “to make the trial if by his instruction I might not become a useful singer for his winter concerts and oratorios”. Caroline eventually left Hanover on 16 August 1772. At Bath she took on the responsibilities of running William’s household, and learning to sing. William had established himself as an organist and music teacher and became fairly busy organising public concerts. Caroline did not blend in with the local society and made few friends, but took several singing lessons a day from William. She became the principal singer at his oratorio concerts, and acquired a solid reputation as a vocalist but declined to sing for any conductor but William. When William became increasingly interested in astronomy, transforming himself from a musician to an astronomer, Caroline again supported his efforts. In particular the two became known for developing high performance telescopes (see the accompanying image). Caroline spent many hours polishing mirrors and mounting telescopes in order to maximize the amount of light captured. She learned to copy astronomical catalogues and other publications that William had borrowed. She also learned to record, reduce, and organise her brother’s astronomical observations. She recognised that this work demanded speed, precision and accuracy. She said somewhat bitterly, in her Memoir, “I did nothing for my brother but what a well-trained puppy dog would have done, that is to say, I did what he commanded me.” It is clear, however, from the independent work she did during William’s lifetime, from her work after William’s death, and from the interest in astronomy displayed in her letters throughout her life, that Caroline was as interested in astronomy as her brother. In 1782, William accepted the office of King’s Astronomer to George III and moved to Datchet and subsequently to Observatory House near Slough (then in Buckinghamshire, now in Berkshire). During this time William perfected his telescope making, building a series of ever larger devices that ultimately ended with his famous 40-foot (12 m) focal length instrument. Caroline was his constant assistant in his observations, also performing the laborious calculations with which they were connected. At William’s suggestion, Caroline began to make observations on her own in 1782. During her leisure hours she occupied herself with observing the sky with a 27-inch (690 mm) focal length Newtonian telescope and by this means detected a number of astronomical objects during the years 1783–87, including most notably an independent discovery of M110 (NGC 205), the second companion of the Andromeda Galaxy. During 1786–97 she also discovered eight comets, her first comet being discovered on 1 August 1786. She had unquestioned priority as discoverer of five of the comets and rediscovered Comet Encke in 1795. In 1787, she was granted an annual salary of £50 (equivalent to £5,700 in 2016) by George III for her work as William’s assistant. She became the first woman in the UK to receive a salary for services to science. This salary became more important the following year when William married a rich widow, Mary Pitt (née Baldwin). The union caused tension in the brother-sister relationship. Caroline lost her managerial and social responsibilities in the household and accompanying status. According to her memoir, she also moved from the house to external lodgings, returning daily to work with her brother. She no longer held the keys to the observatory and workroom, where she had done much of her own work. In later life however, she and Lady Herschel exchanged affectionate letters and she became deeply attached to her nephew, astronomer John Herschel. In 1797 William’s observations had shown that there were a great many discrepancies in the star catalogue published by John Flamsteed. William realised that he needed a proper cross-index to properly explore these differences but was reluctant to devote time to it at the expense of his more interesting astronomical activities. He therefore recommended to Caroline that she undertake the task. The resulting Catalogue of Stars was published by the Royal Society in 1798 and contained an index of every observation of every star made by Flamsteed, a list of errata, and a list of more than 560 stars that had not been included. Caroline returned to Hanover in 1822 following her brother’s death, continuing her astronomical studies to verify and confirm William’s findings and producing a catalogue of 2500 nebulae to assist her nephew John Herschel in his work. In 1828 the Royal Astronomical Society presented her with their Gold Medal for this work – no woman would be awarded it again until Vera Rubin in 1996. The Royal Astronomical Society elected her an Honorary Member in 1835 one of the first women members. After her brother died in 1822, she was grief-stricken and moved back to Hanover, Germany. Caroline Herschel died at Hanover on 9 January 1848 age 98. She is buried at 35 Marienstrasse in Hanover at the cemetery of the Gartengemeinde. The asteroid 281 Lucretia (which was discovered 1888) was named after Caroline’s second given name, and the crater C. Herschel on the Moon is named after her. Sometime ago we reviewed a book about the lives of Willam and Caroline Herschel. You can read it at http://dx.doi.org/10.1063/1.1825271

Date in History: 16 March 1750