Tuesday, March 16, 2010

I swept from ten till one

Today marks 260 years since the birth of the German astronomer, Caroline Herschel. A remarkable woman - in her 70s she was awarded a Gold Medal by the (British) Royal Astronomical Society and no woman would be awarded it again for more than 150 years. Chiefly remembered for discovering comets, she spent much of her life working with and supporting her astronomer brother, Wilhelm, who discovered Uranus. Intermittently, Caroline kept diaries or day-books - extracts from which are freely available online - and these give a lively picture of her unusual lifestyle, such as when she says: ‘I swept from ten till one.’

Caroline was born on 16 March 1750 in Hanover at a time when the crowns of England and Hanover were united under George II. Her parents were musical, as was her older brother, Wilhelm, who moved to England aged 19. In 1772, a few years after her father died, Caroline joined Wilhelm in Bath where he worked as an organist and music teacher. He also organised public concerts in which Caroline soon became the principal singer.

But over the next decade the lives of the two siblings swung away from music and towards her brother’s hobby of astronomy. Wilhelm is credited with discovering Uranus in 1781, and the following year he was appointed King’s Astronomer to George III. Caroline, as his dedicated assistant, was awarded a stipend of £50 a year. When, in 1788, her brother married a rich widow, Caroline began to work more on her own initiative, making many significant observations and calculations, and becoming an authority in her right. Most notably she independently discovered the dwarf elliptical galaxy known as M110, although Charles Messier had observed it some years earlier, and she discovered eight comets (on five of which she has unquestioned priority).

Caroline returned to Hanover in 1822, according to Wikipedia, following her brother’s death, but did not abandon her astronomical studies, continuing to verify and confirm Wilhelm’s findings and producing a catalogue of nebulae to assist her nephew John 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; and in 1835 she and Mary Somerville were granted honorary membership - thus becoming the Society’s first ever women members. Caroline died, age 97, in 1848. Further information can found at the Herschel Museum of Astronomy, Biographies of Women Mathematicians, or Cometography.com.

There are a few published biographies of Caroline Herschel, the most recent of which is The Comet Sweeper: Caroline Herschel’s Astronomical Ambition by Claire Brock (see Amazon.co.uk). However, there is also a much older biography put together by the wife of her nephew John - Memoir and Correspondence of Caroline Herschel by Mrs John Herschel with portraits - and published by John Murray in London in 1876. This uses extensive extracts from Caroline’s diaries and workbooks, and is freely available online. Here are a few of those extracts leading up to the discovery of her first comet.

18 July 1786
‘I spent the whole day in ruling paper for the register; except that at breakfast I cut out ruffles for shirts. Mr. and Mrs. Kelly and Mrs. Ramsden (Dollond’s sister) called this evening. I tried to sweep, but it is cloudy, and the moon rises at half-past ten.’

19 July 1786
‘In the evening we swept from eleven till one.’

20 July 1786
‘Prince Charles (Queen’s brother) Duke of Saxe-Gotha and the Duke of Montague were here this morning. I had a message from the King to show them the instruments.’

24 July 1786
‘I registered some sweeps in present time and Pole distance. Prince Resonico came with Dr. Shepherd to see the instruments. I swept from ten till one.’

28 July 1786
‘I wrote part of Flamsteed’s Catalogue in the clear. It was a stormy night, we could not go to bed.’

29 July 1786
‘I paid the smith. He received to-day the plates for the forty-foot tube. Above half of them are bad, but he thinks there will be as many good among them as will be wanted, and I believe he intends to keep the rest till they return. Paid the gardener for four days which he worked with the smith. I registered sweeps to-day. By way of memorandum I will set down in this book in what manner I proceed.

I began some time ago with the last sweep which is booked in the old register (Flamsteed’s time and P. D.), viz., 571, and at different times I booked 570, 569, 568, 567, 566, 565. To-day I booked 564; 563 is marked not to be registered; 560 and 561 I was obliged to pass over on account of some difficulty. The rest of the day I wrote in Flamsteed’s Catalogue. The storm continued all the day, but now, 8 o’clock, it turns to a gentle rain.’

30 July 1786
‘I wound up the sidereal timepiece, Field’s and Alexander’s clocks, and made covers for the new and old registers.’

31 July 1786
‘I booked 558, 557, and 554; 556, 555, I was obliged to leave out on account of some difficulty.’

‘Mem: I find I cannot go on fast enough with the registering of sweeps to be serviceable to the Catalogue of Nebulae. Therefore I will begin immediately to recalculate them, and hope to finish them before they return. Besides, I think the consequences of registering the sweeps backwards will be bad.’

1 August 1786
I have counted one hundred nebulae to-day, and this evening I saw an object which I believe will prove to-morrow night to be a comet.

2 August 1786
‘To-day I calculated 150 nebulae. I fear it will not be clear to-night. It has been raining throughout the whole day, but seems now to clear up a little.

1 o’clock. The object of last night is a comet.’

3 August 1786
‘I did not go to rest till I had wrote to Dr. Blagden and Mr. Aubert to announce the comet. After a few hours’ sleep, I went in the afternoon to Dr. Lind, who, with Mr. Cavallo, accompanied me to Slough, with the intention of seeing the comet, but it was cloudy, and remained so all night.’

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