The Most Important Woman in the History of Astronomy [read this tribute including the informative appendices at the end] and she was born on 11 December >!today!< 1863. I mentioned Cannon in passing when I wrote about Mina Fleming who was the first woman hired by Edward Pickering the director of the Harvard Observatory. Fleming in turn had a major say in hiring the 'harem' of female astronomers, including AJC, to carry out a supremely ambitious project in cataloging every visible star. I don't mean the trivial task of identifying every star visible with the naked eye on a clear moonless night because that's a number rather less than 10,000. You shouldn't try for too much accuracy on that count because we all have different retinas and atmospheric conditions will blank out the faintest stars in a random way.
AJC was the best of these "Harvard Computers" and she is credited with cataloging something close to 400,000 stars. There are about 50,000 hours available for nocturnal telescope work in a 20 years working life, so there wasn't a lot of time for tea-breaks. Although it must be said that AJC was a pioneer in bringing the power, reproducibility and permanent record of photography to the field of astronomy. The business model was that the men would do the heavy lifting with pointing the enormous telescopes to the next portion of the sky and then press the button that took the photograph that had been filtered through a prism to expose the several wavelengths of light emitting from the source star. It was left to the women to process these hundreds and the thousands of images into the massive catalogue that they were compiling. Nobody ever clocked as many stars as AJC. I say 'business model' advisedly because Pickering quite consciously hired women because they were much cheaper to employ than men but he further de-gilded the lily by paying them less than a female secretary. The work may have been fascinating (sounds far too dull and repetitive for my butterfly mind) but I can imagine that the cameraderie and sense of cosmic purpose must have provided their own compulsion to keep so many smart young women in the project for so long.
Mary Lyon sensibly ordering the already available data as her claim to fame, AJC is most famous for knocking into shape the method of cataloguing stars by their position but also into bins or similarity. Originally they had been shoe-horned into boxes based on how pronounced were the dark Fraunhofer lines that could be seen in their spectra and labelled alphabetically with A having the darkest bands, B fainter etc. Mina Fleming, the Curator of the Harvard collection developed this catalogue with the boss Pickering. But it seemed too clumsy to Antonia Maury, who was the niece of Henry "The Money" Draper, and she developed a more complex/subtle classification. But AJC noted “The evidence that the Orion spectra [Class B] precede the Sirian [Class A] is as good as that the Sirian precede the solar [Class G]". Accordingly she was able to broker a deal between the two competing protocols which took something from each and this compromise ordering O B A F G K M [see the far-blue segment L] reflects the evolution of the properties of the stars while mangling the alphabetical order in a way similar to the QWERTY keyboard (d'accord, d'accord aussi comme l'ASERTY clavier) on my typewriter, which has fossilised traces of its original alphabetical ordering. The BAFfling order required the mnemonic in the title which was also invented by AJC. It transpires that the OBAFGKM order tracks rather well the real temperature of the stars, an attribute which is only roughly correlated with darkness of the bands = the amount of hydrogen present.
Her innate sense of empathy was what enabled her, and perhaps her alone, to reconcile two positions strongly held by forceful personalities. She was interested and interesting, and listened to what people would say to her and seems to have had her selfishness genes shot off in the war: "priceless ability of being good company for all kinds of people ... her character, distinguished by modesty and unselfishness, was human nature at its best". It is incredible how well she did for herself and by extension what she did for enhancing the status of women in science. It might be noted that, as well having the usual handicap of XX chromosomes, she contracted scarlet fever while a student and finished up deaf from that assault. In 1932, after she won the Ellen Richards prize from the Association to Aid Scientific Research by Woman, the prize was disbanded because the committee felt that equality had been achieved. Ask any woman trudging through corporate science today 80+ years later if she thinks this is true. Nope, AJC didn't think so either and donated her prize money to start funding the Annie Jump Cannon Award in Astronomy which gives ($5000!!) annually to a young woman astronomer. The award is a fitting tribute to one who had surpassing generosity of spirit. There is no fitting tribute to someone who worked so hard for so long at the unsexy essential infrastructure of her field, except "bonnets off!"