She made a decision that "went against her ancestors' teachings" and then advanced a discipline by decades.

In "He was a doctor, but he changed astronomy", the author details Draper's life as an astronomer. His achievements were inseparable from the support and collaboration of his wife Anna. After Draper's death, in order to commemorate her husband and complete their unfinished work with the highest efficiency, Anna continued to fund an astronomy team at the Harvard Observatory for 28 years until his death. In the end, the Harvard Observatory obtained spectra of more than 200,000 stars, classified them and compiled them into the famous "Henry Draper Star Catalog". Anna's foresight and generosity have greatly promoted the development of astronomy and cosmology. With her support, many Harvard female computer workers have grown into outstanding astronomers, creating the glory of the Harvard Observatory. Her name shines with the stars.

Written by | Wang Shanqin

In the field of astronomy (including astrophysics), the Henry Draper Catalogue, named after Henry Draper (1837-1882), is an important term that cannot be avoided. The Draper Catalogue records the spectra and brightness of hundreds of thousands of stars. It is a huge treasure trove for human understanding of stars and has an important impact on almost all branches of astronomy.

However, the Draper Catalog was not compiled by Henry Draper himself. So why is this catalog named after Draper? This is a tortuous but magnificent story.

A forgotten female scientist

In the history of science, there is a special group of women who assisted their husbands or male relatives in scientific research, but they were not regarded as collaborators in the relevant research and are therefore often nameless or only mentioned occasionally.

Anna Palmer Draper (1839-1914), the wife of Henry Draper (hereinafter referred to as "Draper"), was a member of this special group.

Anna was born Mary Anna Palmer on September 19, 1839 in Stonington, Connecticut. Her father, Courtlandt Palmer (1800-1874), was a wealthy lawyer, businessman and real estate investor, and her mother was Mary Ann Suydam (1812-1867).

Portrait of Anna Anna Palmer. │Source: John White Alexander (1856-1915)

Anna's father, Palmer Sr., was born in Stonington and moved to New York when he was a teenager. He later became wealthy by investing in real estate. He then invested in railroads and served as president of the Providence and Stonington Railroad. He was also one of the founders of the Safe Deposit Company of New York and a director of several business companies. [1] These business investments made him one of the richest people in New York.

Anna grew up in a mansion on Madison Avenue in New York City, which was built by Palmer Sr. She had an older brother, Richard Suydam Palmer (1834-1870) and a younger brother, Courtlandt Palmer Jr. (1843-1888).

In 1867, 28-year-old Anna married 30-year-old Draper, dropping her first name "Mary" and taking her husband's surname. After the marriage, Anna immediately became Draper's assistant. In order to devote as much time as possible to scientific research, their honeymoon trip only went as far as lower Manhattan. Their purpose there was to buy a glass mirror blank. [2] The couple ground, polished, and silvered it to make it the primary mirror of a 28-inch (71 cm) telescope.

The mansion where Anna had lived since childhood also became the couple's joint property. They converted part of it into a laboratory and workshop, and used the other part to hold science salons and popular science lectures (which could accommodate 200 listeners[3]).

When they needed to observe the stars, they would go to the observatory in Hastings and rest at their home in Dobbs Ferry, two miles away. [3] Draper would accompany him on every observation. When they were doing work that did not require observing the night sky (such as analyzing photographic film, conducting spectroscopy research, and polishing telescope lenses), they would work together at their home in New York.

When the couple first got married, wet plate photography was the main method of photography. To take photos of celestial bodies, negatives had to be made quickly before observation to prevent the wet plate from drying out and becoming ineffective during photography. One of Anna's tasks was to apply colloidal tincture on the glass plate before observation to make wet plate negatives, and then take photos together. [3, 4] After dry plate photography technology matured, the couple actively made dry plate negatives, which were managed by Anna. [4]

In 1872, the 28-inch telescope was completed, and Anna assisted Draper in taking photos of the spectrum of Vega with it. The spectrum of Vega they obtained showed obvious absorption line characteristics. This was the first time that humans had photographed a star spectrum showing absorption lines. From then on to 1882, Anna assisted Draper in taking high-quality spectra of 78 stars and planets using more than 100 glass plates.

Draper's 28-inch (71 cm) reflecting telescope and a 12-inch (30.5 cm) refracting telescope on the same mount. Image credit: Hastings Historical Society

On May 10, 1874, Anna's father died, leaving a huge inheritance, of which she, her brother's descendants (her brother had died in 1870) and her younger brother each inherited a portion.

During the total solar eclipse on July 29, 1878, Anna volunteered to keep time and count for Draper and the others in the tent to prevent others from miscalculating the duration of the eclipse because they were concentrating on watching the total eclipse. [3] As a result, she became the only person in the eclipse expedition who did not witness the total eclipse.

On September 30, 1880, Anna assisted Draper in photographing the Orion Nebula (M42) with an 11-inch telescope. They were the first to photograph this nebula. In 1881, Anna assisted Draper in photographing the tail of the "Great Comet of 1881" and obtained the first spectrum of the comet's head.

From 1867 to 1882, Anna worked side by side with her husband for 15 years. She not only served as Draper's assistant, but also became an outstanding female scientist in her own right. However, she always participated in the collaboration as an uncredited assistant, which made her identity as a female scientist ignored by most people (especially later generations) - although she was elected as a member of the Astronomical Society of the Pacific. [4]

For Anna, the real misfortune was not that her identity as a scientist was ignored - she didn't care about that, but the untimely death of her husband: on November 20, 1882, Draper died of illness at the age of 45.

Draper's sudden death not only hit Anna hard, but also abruptly interrupted the couple's grand plan to take a large number of stellar spectra and classify them.

Seeking cooperation for business investment

Despite the ongoing grief, Anna decided to continue her husband's unfinished work. At first, she planned to buy the property of the observatory built by Draper (the property belonged to Draper's father, who gave it to his sister, Draper's aunt, before his death), so that she could actually own the observatory and then name it "Henry Draper Astronomical and Physical Observatory".

In order to continue her work of photographing and analyzing star spectra, she decided to hire two assistants, one to photograph the spectra of stars and the other to analyze the spectra and compare them with those of other celestial bodies. However, she could not find an assistant that satisfied her.

At the same time, Anna hoped to fund a professional team in the field of astronomy and obtain their assistance. The news that Anna planned to seek cooperation quickly spread. Alvan Clark (1804-1887), a famous telescope maker, was one of the first people to know the news. Draper had bought a telescope from him, and the couple was familiar with him.

This news soon spread from Clark to the famous astronomer Edward Pickering (1846-1919), who was the director of Harvard College Observatory (hereinafter referred to as "Harvard Observatory") at the time.

Pickering between 1880 and 1890. │Source: Mondadori Publishers

Pickering had previously admired Draper's work in astronomical photography, and the two became members of the National Academy of Sciences. When the Drapers hosted their scientific colleagues at their home in New York, Pickering also participated. As a result, he became good friends with the Drapers.

In January 1883, Pickering wrote to Anna, saying: "Dear Mrs. Draper, Mr. Clark (a famous telescope maker) told me that you were preparing to complete the work of Dr. Draper. I am very interested in this matter, which is why I mentioned this to you." [5] (The parentheses in the quotation are original text, the same below.)

Pickering expressed his admiration for Anna's plan, acknowledging and emphasizing the difficulty of its realization. He then concluded his letter by adding: "I shall be very glad if I can do anything to honour the memory of a friend whose talents I have always admired." [5]

Some sources say that Anna wrote to Pickering, seeking help and cooperation. However, based on the content of the letter and the time difference (only about 2 months passed from Draper's death to Pickering's writing of the letter), the author speculates that Pickering took the initiative to write to Anna to seek cooperation after hearing the news.

Anna immediately wrote back to thank Pickering for his "kind and encouraging letter." [5] After that, the two frequently exchanged letters to discuss specific matters of cooperation. With Pickering's encouragement, Anna sorted out Draper's posthumous works, and Pickering and his collaborators wrote a paper based on Draper's results and published it in 1884 [6] (Draper and Anna were not named).

In 1885, Pickering combined the object end prism technology with astronomical photography for the first time, which enabled him to photograph the spectra of dozens or even hundreds of stars on the same film. This meant that the time was finally ripe for batch photography of stellar spectra. Pickering immediately launched a plan to photograph stellar spectra in batches. In May 1885, he wrote to Anna to tell her about the plan, hoping that she would be interested in it and provide financial support.

Anna also immediately realized the great potential of this new technology and agreed to use her inheritance to fund Pickering's team, allowing the latter to use collective strength to photograph and classify the spectra of a large number of stars. Anna is the daughter of a wealthy businessman. She was influenced by her father while growing up, so she has a shrewd and rational business mind. She did not directly transfer money because of excitement, but planned the funding of the project through detailed negotiations. In the following months, she had been communicating with Pickering on the allocation and use of funds.

According to Pickering's later recollections, during the negotiation process, Anna gave many important scientific suggestions, such as: how to keep the instruments of Harvard Observatory working continuously, especially how to make some of them work all night on clear nights; how to recruit a large number of computer workers to speed up data processing; how to publish the compiled star catalog in a suitable form, etc. These details all reflect Anna's professional ability as a scientist.

A decision that goes against ancestral teachings

On February 14, 1886, Anna reached an agreement with Harvard Observatory represented by Pickering in her reply letter to establish the Henry Draper Memorial Fund (hereinafter referred to as the Draper Fund). This fund will support the team led by Pickering to fulfill Draper's last wish - to photograph and classify a large number of stellar spectra.

There was no precedent in her family for donating inheritance to astronomical institutions, so Anna's decision could be said to be "against the family's teachings." Even she herself did not expect how far-reaching the impact of her donation would be on astronomy and cosmology.

According to the plan, Pickering will use the Draper Fund to recruit more people and purchase glass plates for photography. These people will take spectra of 100,000 stars and classify them. These stars are no dimmer than magnitude 9. The dimmest star that most people can see is magnitude 6, and the brightness of a magnitude 9 star is 6.3% of that of a magnitude 6 star. According to the agreement, the name of this star catalog that later went down in history was the "Henry Draper Catalogue".

This is an unprecedented and ambitious project. The funds are paid in installments. This is the model that Anna and Pickering had agreed on before. It is conducive for her to regularly inspect the progress of the project and stop funding if it is not as expected. This is undoubtedly a spur to Pickering's team. Within one week after the agreement was signed, Anna sent $1,000 as the start-up fund for the project and promised to pay it regularly thereafter. (At that time, $1 is equivalent to $32 today.)

Classifying the spectra of hundreds of thousands of stars

Before Pickering received the donation, there were six female computer workers at Harvard Observatory, and not all of them belonged to Pickering's team. With the funds paid in installments by Anna, Pickering hired more female computer workers. They mainly worked on the spectral classification of stars and compiled the results into the Draper Catalog.

In Pickering's team, male astronomers were responsible for observing and photographing stars, while female computer operators were responsible for analyzing photographic plates, classifying and cataloguing the spectra of stars. Draper's niece Antonia Maury (1866-1952) was also a member of the team.

At the beginning of the project, Anna still had high hopes for the observatory used by Draper during his lifetime, hoping to complete the Draper Catalog in collaboration with the Harvard Observatory. [6] However, the rapid progress of the Harvard Observatory made Anna realize that only the Harvard Observatory could accomplish this feat. In addition, she was unable to recruit satisfactory assistants who could work in the Draper Observatory. Therefore, she decided to hand over the entire project to the Harvard Observatory.

In 1887, Pickering proposed that a 28-inch telescope would help to confirm the type of star spectrum more quickly, and Anna generously donated it (her favorite telescope) to the Harvard Observatory. In addition, Anna also donated the 11-inch (28 cm) and 15.5-inch (39 cm) telescopes that Draper had used to the Harvard Observatory. The Harvard Observatory used the Draper Fund to build a special dome to house these telescopes.

A photo of Harvard Observatory taken around 1900 (colored later). The three buildings in the front were built by Harvard Observatory to house the Draper donated by Anna and the three telescopes she used. │Source: Harvard College Observatory, Tom Fine

A photo of the 11-inch refracting telescope used by Draper after it was installed at Harvard Observatory. │Source: Harvard College Observatory

The original records "unearthed" in 2015 show that Anna also shared with Harvard Observatory the chemical process formula that Draper had previously used to silver the 28-inch telescope. She also donated Draper's notebooks and photographic negatives to Harvard Observatory.

A notebook from the PHAEDRA project showing Anna's contribution to the silvering of the telescope. Image source: Wolbach library, CfA

In order to speed up the project, Anna also purchased a new 8-inch (20.3 cm) telescope and a matching object end prism and donated them to the Harvard Observatory. This telescope was called the "8-inch Draper Telescope." [6]

The 8-inch refracting telescope Anna donated to Harvard Observatory. │Source: Harvard College Observatory

After the task of stellar spectrum classification was handed over to Harvard Observatory, Anna basically stopped doing research due to poor health and other reasons, and focused her main energy on holding scientific lectures and exhibitions at her home. However, she would go to Harvard Observatory regularly to learn about the progress of the work. During this period, she became friends with female calculators such as Williamina Fleming (1857-1911) and Annie Cannon (1863-1941).

In 1886, Pickering's team photographed and classified the spectra of 5,400 stars no fainter than magnitude 6 and 2,400 stars fainter than magnitude 6. In 1890, Pickering published the first edition of the Henry Draper Star Catalog, which included the classification of 10,498 star spectra by Fleming and other female calculators. In 1897, Maury and Pickering collaborated to publish a classification of the spectra of 681 bright stars in the northern sky. In 1901, Cannon and Pickering published a classification of the spectra of 1,122 bright stars in the southern sky.

Anna was very pleased with all these developments. Whenever the Harvard computer confirmed a new type of spectrum, Pickering and others would show it to Anna, and she would be very excited every time. [3]

In 1887, the second year after the project was established, she decided not to limit her goal to the photography and classification of stellar spectra, but to expand her goal to the observation of all stellar phenomena,[3] such as the magnitude of stars, and especially the observation of variable stars.

Fleming (standing far right) shows Anna (second from the right, sitting at the table) the progress of the Draper Catalog. The others in the picture are all Harvard female calculators. │Source: Center for Astrophysics/Harvard & Smithsonian

A monument to astronomy

Cannon and other Harvard female computer workers spent four years classifying the spectra of a large number of stars and merging them with the spectral library of previously confirmed stars to compile a complete version of the Henry Draper Star Catalog.

The catalog contains the positions, magnitudes, and spectral classifications of 225,300 stars not fainter than magnitude 9. From 1918 to 1924, the complete Henry Draper Catalog was published in nine volumes as the Annals of the Astronomical Observatory at Harvard College.

The frontispiece and title page of the first volume of the Draper Catalog. The illustration shows the seven typical spectra of stars determined by Harvard University female calculator Cannon and others: O, B, A, F, G, K and M. │Source: Annals of the Astronomical Observatory of Harvard College, volume 91, 1918 (Linda Hall Library)

Anna did not live to see the moment when this feat was finally completed - she died of illness on December 8, 1914, at the age of 75. However, she would have no regrets, because before her death, the then-unpublished Henry Draper Star Catalog had included about 200,000 stars[3], twice the number previously planned.

From the establishment of the Draper Fund in 1886 to her death in 1914, she spent 28 years watching the rapid expansion of the Henry Draper Catalog. Pickering did not let her down, and her efforts were enough to comfort her husband who died young.

To express gratitude and remembrance for Anna, the third volume of Henry Draper's Star Catalog, published in December 1918, used Anna's portrait as the frontispiece. In a brief preface of only 7 lines, Pickering explained the origin of the project and said, "Hence, it is very appropriate to use her [Anna] portrait as the frontispiece of this volume..." At this time, Pickering had also entered the countdown of his death.

Portrait of Anna in the frontispiece of Volume 3 of Henry Draper's Star Catalog. │Source: Linda Hall Library

On February 3, 1919, Pickering, who had worked hard all his life, died (he did not wait until the third volume of the Draper Catalog was published), and Cannon was responsible for the publication of the next six volumes of the Henry Draper Catalog. In 1921, Harlow Shapley (1885-1972) became the new director of the Harvard Observatory.

Despite Shapley's flawed character, he continued to support Harvard Observatory's work in stellar spectral classification. Cannon led a group of female computer workers to compile an extended table of the Henry Draper Star Catalog, which included the spectra of 46,850 stars between magnitude 9 and 11 in some parts of the sky (the brightness of a star of magnitude 11 is about 1/6 of that of a star of magnitude 9).

Finally, the Henry Draper Catalog and its extensions included spectra of 359,082 stars. The glass plates used to make the Henry Draper Catalog reached 120 tons, which are still preserved at the Harvard Observatory.

The Henry Draper Catalog was the first to achieve the ambitious goal of cataloguing and classifying the spectra of hundreds of thousands of stars, which rapidly matured the classification of stellar spectra. The Draper Catalog made an epoch-making contribution to human understanding of the nature of stars, and has benefited astronomers ever since.

The "Harvard classification" (a one-dimensional classification) that Cannon developed in the process of compiling the Henry Draper Catalog quickly became the standard classification system that continues to this day, with only minor modifications.

The more complex classification rules given by Maury laid the foundation for the subsequent two-dimensional classification of stellar spectra (color-luminosity), and inspired Ejnar Hertzsprung (1873-1967) to obtain the "Hertzsprung-Russell diagram", which is recognized as one of the cornerstones of stellar physics.

A Hertzsprung-Russell diagram based on the color and temperature values ​​of 22,000 stars in the Hipparcos Catalogue and 1,000 red dwarfs and white dwarfs in the Gliese Catalogue. Image source: Richard Powell

While pursuing her doctoral degree at Harvard University, Cecilia Payne-Gaposchkin (1900-1979) studied the stellar spectrum photographs provided by Cannon. Combined with theoretical calculations, she proposed for the first time in her doctoral thesis completed in 1925 that most of the matter in stars and the entire universe is hydrogen.

The Henry Draper Catalog, which Anna helped to create, is a monument to astronomy, and even at the most conservative level, we can say that Anna's funding advanced the field of stellar physics by decades.

In fact, the project Anna initiated had an impact on more than just stellar physics. In a 1991 article reviewing the development of the Draper Catalog, astronomer and historian of astronomy Dorrit Hoffleit (1907-2007) said: "There is hardly a branch of astronomy that has not benefited from the work of the Henry Draper Memorial [Fund]. Without the vision and generosity of Mrs. (Anna) Draper, it is not known whether the Harvard [Observatory] of the days of Pickering and Shapley would have become so outstanding."

Anna's funding for Pickering's team also promoted the development of cosmology. Henrietta Swan Leavitt (1868-1921), a female computer in Pickering's team, discovered the period-luminosity relationship of Cepheid variables; Hubble (Edwin Powell Hubble, 1889-1953) used this relationship to determine the distances of dozens of galaxies, and combined with the recession speed of some galaxies previously measured by Vesto M. Slipher (1875-1969), confirmed that "the recession speed of galaxies is proportional to the distance." This result means that the universe is expanding (although Hubble himself did not think so), which eventually gave birth to the Big Bang cosmology.

The loving mother of a Harvard computer

Anna's funding provided a crucial foundation for the development of female astronomers such as Fleming, Cannon, Maury and Leavitt. Pickering used the funds provided by Anna to pay their salaries, enabling them to concentrate on their work at the Harvard Observatory and become excellent astronomers. 100 years ago, when it was generally difficult for women to enter the scientific community, Anna and Pickering made them successful. Pickering was their strict father and Anna was their loving mother.

They also represented the "Harvard Computers" and won the admiration of astronomers and many media around the world. Harvard Observatory was not the only astronomical institution to employ female computers, but Harvard Computers was the most famous female research group in the field of astronomy.

After Pickering's death, every time Harvard Observatory recruited low-paid or even unpaid female computer workers, there were snowflakes of job applications from all over the world. These job-seeking women considered it a great honor to be able to work here, and they firmly believed that this was the best training for them. It was Anna's funding and Pickering's leadership that made the female computer workers at Harvard Observatory a symbol of honor and achievement.

Henry Draper Medal

Anna was also the founder of the Henry Draper Medal, which she established in memory of her husband by donating funds to the National Academy of Sciences in 1886.

The Draper Medal was initially awarded for research in the two fields of spectroscopy and radiation research, and later the scope of the award was expanded to include outstanding original research in the entire field of astronomy and the closely related field of physics.

Draper Medal. │Source: National Academy of Sciences

Samuel Langley (1834-1906), who studied solar radiation, became the first Draper Medal winner in 1886. Pickering became the second Draper Medal winner in 1888, and William Huggins (1824-1910), Draper's rival and friend during his lifetime, became the sixth Draper Medal winner in 1901. Cannon, Anna's friend and the main compiler of the Draper Catalog, became the 21st Draper Medal winner in 1931.

Before 1985, the Draper Medal was awarded every 1-6 years, with irregular intervals. Since 1985, the Draper Medal has been awarded every 4 years. To date, the award has been given 50 times, and only 56 astronomers or physicists have won the Draper Medal. The winners are many masters, and 9 of them have won the Nobel Prize in Physics before or after receiving the award. [7] The Draper Medal has thus become one of the major awards in the field of astronomy.

Her name shines with the stars

From the time she gave the first grant in 1886 until her death, Anna donated a total of $250,000 to the Harvard Observatory. In addition, she left an estate of $150,000 to the Harvard Observatory through her will to be used for the maintenance and research of hundreds of thousands of negatives. [2] This $400,000 is equivalent to $12 million today.

In an era when the trend of state-sponsored scientific research was not yet popular and the relevant systems were not yet perfected, private sponsorship played a vital role in the research of some institutions and individuals, and private sponsorship often directly determined the life and death of a project.

After Anna's death, her large collection of artifacts, antiques, tapestries, miniature paintings, and other works of art were donated to the Metropolitan Museum of Art. The 28-inch telescope Anna donated to Harvard Observatory is still at Harvard University. The 11-inch telescope she donated to Harvard Observatory was given to China (located in Beijing) by the latter in 1947, but was lost due to the war. The 8-inch telescope she donated to Harvard Observatory was given to Poland, where Polish astronomers continued to use it to study object end prism spectra for many years. [6]

As Cannon wrote in his 1915 article in Science magazine honoring Anna, "Her name will forever be proudly connected with the science of astrophysics."[3]

Her name, Anna Palmer Draper, shines like a star.

Main references

[1] http://famousamericans.net/courtlandtpalmer/

[2] https://www.lindahall.org/about/news/scientist-of-the-day/mary-anna-palmer-draper

[3] Cannon, Annie J. Mrs. Henry Draper, Science, 1915, 41, 1054, 380-382

[4] https://aas.org/posts/news/2022/10/month-astronomical-history-september-2022

[5] https://storymaps.arcgis.com/stories/c7f380fd6a784f94a0fbb0303ef8adae

[6] Hoffleit, Dorrit, The evolution of the Henry Draper memorial, Vistas in Astronomy,1991, 34, 1, 107-162

[7] http://www.nasonline.org/programs/awards/henry-draper-medal.html

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