The Comet Sweeper (Icon Science): Caroline Herschel's Astronomical Ambition

By Claire Brock

Having escaped domestic servitude in Germany by teaching herself to sing, and established a career in England, Caroline Herschel learned astronomy while helping her brother William, then Astronomer Royal.



Soon making scientific discoveries in her own right, she swept to international scientific and popular fame. She was awarded a salary by George III in 1787 – the first woman in Britain to make her living from science.



But, as a woman in a male-dominated world, Herschel's great success was achieved despite constant frustration of her ambitions. Drawing on original sources – including Herschel's diaries and her fiery letters – Claire Brock tells the story of a woman determined to win independence and satisfy her astronomical ambition.

• Language: English
• Publisher: Icon Books
• Release date: Jan 5, 2017
• ISBN: 9781785781674

Reviews for The Comet Sweeper (Icon Science)

[setnahkt · Rating: 3 out of 5 stars]

Claire Brock’s biography of Caroline Herschel has a problem similar to the biography of the Marquise Du Châtelet reviewed a while back; Ms. Brock, an English professor, really doesn’t communicate enough about astronomy to explain Caroline Herschel’s accomplishments. Instead she falls back on fairly standard arguments – women in the 18th century were oppressed, were denied opportunity, didn’t get the credit they deserved, were forced to be dependent on men, etc. All these things are perfectly true, of course, and should cast additional luster on what Caroline Herschel achieved. Which was:
*Despite being denied an education and turned into a domestic servant by her mother (her father Isaac was supportive but too easy-going to argue with his wife) she taught herself to play the violin.
*Breaking free of Hannover and her now widowed mother’s household on the invitation of her musician brother William, she journeyed to Bath, England, and became an accomplished singer. (Her method for learning to sing seems strange, but was apparently common in the 18th century – she practiced with a gag in her mouth. I’ve seen pictures of that on the Internet, but never realized opera was involved).
*When her brother abandoned his musical career to become an astronomer, Caroline dutifully accompanied him and became his observing assistant, carefully noting positions dictated by William, keeping papers and star catalogs in order, and generally being “invaluable” (in William’s words).
*When not required by William, Caroline took up her own observing program, eventually discovering seven comets.
The problem here is Brock’s explanation of what was involved in 18th century telescopic astronomy is badly muddled. All of William Herschel’s telescopes were reflectors with what we would now call altazimuth mountings, and pretty crude ones at that. (Brock has a hopelessly confused description of the difference between and relative merits of the reflectors and refractors of the time).
Any celestial object observed with the rig had to have its coordinates converted to right ascension and declination (Brock refers to “night ascension” several times; I suspect a misunderstanding except sometimes it’s in direct quotes from one of the Herschel’s letters. Perhaps that’s what they called it then). I have no idea how this was done. Pictures of Herschel’s telescopes don’t seem to have any sort of indices or scales for measuring an object’s position; I can only assume they aren’t visible or have been removed. You can determine right ascension without scales by starting with an object of known position and timing how long it takes the target object to come into view (and there’s a hint it might have been done this way, since Caroline Herschel records consulting the clocks as one of her duties) but declination measurement requires some sort of scale. To get there with an altazimuth mounting you have to have the telescope’s position accurately surveyed (apparently Caroline helped with that too; Brock says she “learned to use rods to measure the ground” without explaining why), know the time of the observation as precisely as possibly, measure the object’s distance above the horizon (ideally, an artificial horizon) or from the zenith or from another object of known position, and do spherical trigonometry. Caroline Herschel was responsible for resolving these observations and making fair copies of the results – William Herschel sometimes called out object positions at the rate of six a minute. Her mathematics, beyond basic arithmetic, was entirely self-taught. This is vastly more impressive than her comet discoveries – which could have been made by anybody with reasonable perseverance.
Ironically, while Brock claims that modern histories have relegated Caroline Herschel to a footnote to her brother’s accomplishments, her contemporaries and near contemporaries were seemingly quite aware of what was involved. Francis Baily, Neville Maskelyne, John Dreyer, and Joseph de Lalande all praised Caroline Herschel’s abilities (de Lalande named his daughter “Caroline” in her honor; he’d named his son “Isaac” after Newton) as an observing assistant; unfortunately Brock only mentions this in passing and almost as if it were sort of a patronizing insult.
Good enough as a straightforward biography but not adequate as a description of 18th century astronomy, regardless of the astronomer’s gender.