I was reading about the discovery of Neptune when I realised that Caroline Herschel was still alive at the time. Neptune was discovered in September 1846. Caroline died in January 1848, more than a year later. Do we have evidence as to whether she knew about Neptune’s discovery? If she did, then do we know anything about her reactions to it?

Wikipedia lists two full length biographies:

  • The Comet Sweeper: Caroline Herschel's Astronomical Ambition by Claire Brock (2007)
  • The Quiet Revolution of Caroline Herschel: The Lost Heroine of Astronomy by Emily Winterburn (2017)

I was able to borrow the first one on the Internet Archive and did a text search but there was no mention of Neptune. I also did a text search on the second book on Google Books and it also does not mention Neptune.

Motivation for the question

The discovery of Neptune came about due to the need to explain irregularities in the orbit of Uranus which had been discovered by Caroline's brother, William Herschel, in 1781, and was notable as the first new planet to be discovered since antiquity. Caroline assisted William in his work and was also a celebrated astronomer in her own right. She maintained an interest in astronomy into her old age, so I thought that the news would have been of considerable interest to her.


1 Answer 1


The answer is yes, she did know. Remarkably she was informed of the news mere days after the discovery in a letter from Alexander von Humboldt dated September 25 1846 which accompanied the Gold Medal presented by the King of Prussia on her 96th birthday. The planet had yet to be named and he refers to it as 'the transuranian planet'. Here is the relevant section from the letter

[The King of Prussia] had wished you to receive this little gratification on your ninety-sixth birthday, and by an unfortunate mistake the date of Caroline Lucretia Herschel’s birth has been changed from the 16th of March to the 16th of October, and I am the culprit, misled by a misprint in a French history of astronomy. I know I may count upon your indulgence and that of your distinguished family in England. I specially deserve such leniency to-day—the day on which my young friend, Dr. Galle, assistant astronomer in our Observatory (to the triumph of theoretical astronomy be it said), has discovered the transuranian planet indicated by Le Verrier as the cause of the perturbations of Uranus.

Caroline clearly read this letter since on 1 October 1846 she wrote to her niece about it although she makes no mention of the new planet

My dearest Niece!—

I must not let the messenger go without a line just to say that I am still in the land of the living, of which, however, I have no other proof than a letter from Baron v. Humboldt, inclosing a Golden Medal from the King of Prussia. I can say no more at present, and the post will not wait, so believe me, my dear niece, yours and my dear nephew’s most affectionate aunt,

                                                                                                                            Car. Herschel.

My quick browse through the Memoir and Correspondence of Caroline Herschel, where I found these letters did not reveal anything about her reaction to the news. However in a letter from her nephew Sir John Herschel dated July 11 1847 which accompanied his “Cape Observations” book, he mentions that Le Verrier is at Collingwood, Herschel's home, so presumably she knew who he was.

Louisa sends you all our news, and the autographs of Struve and Adams, who, with M. Leverrier, are now at Collingwood.

Source: Memoir and Correspondence of Caroline Herschel by Mrs John Herschel (1876)

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    $\begingroup$ Adams is also relevant to this discussion as he also calculated the position of Neptune before it was discovered but not noted until after Leverrier . $\endgroup$
    – mmmmmm
    Dec 1, 2023 at 18:05
  • $\begingroup$ Yes you are right. Thanks for pointing it out. Although my understanding is that there is some controversy over the accuracy of the calculations made by Adams. But at this period he was also associated with the discovery so it seems significant that Herschel mentions both Adams and Le Verrier together. $\endgroup$
    – Krishna
    Dec 1, 2023 at 18:22
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    $\begingroup$ Ah I went to Cambridge University and have looked through the telescope that Challis first saw Neptune based on Adams' calculations but did not recognise it at the time - so I might be biased $\endgroup$
    – mmmmmm
    Dec 2, 2023 at 10:24

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