Annie Jump Cannon: Classifying the Stars

Raised to Love Science

Born on December 11th in 1863, Annie grew up the oldest child of three in Dover, Delaware. As a little girl, her mother taught her a love of science and to pursue her dreams. They would sit together in their attic at night with an old astronomy textbook identifying constellations and naming stars by candlelight.

Following her mother’s advice, Cannon pursued an education at Wellesley College, studying physics and astronomy. After she graduated, she returned to Delaware and learned photography, a new art form at the time. She traveled through Europe with her Blair Box Camera, chronically her adventures for a pamphlet called “In the Footsteps of Columbus.” She also spent time traveling to view solar eclipses around the globe.

After about ten years of peaceful living, photography, and travel, Cannon suffered from several hardships one after the other. Her hearing was damaged, possibly due to a bout of scarlet fever, and her mother passed away. She became very focused on her work and asked for a job at her alma mater, Wellesley, eventually becoming a professor.

She later enrolled at Radcliffe College, a coordinate institution to Havard University, which only accepted male students at the time. This gave her access to the Harvard Observatory and an opportunity that would change her life and the science of astronomy.

Computer: Analyzing Glass Plates

In 1850, the first photograph of a star outside of our solar system was recorded on a glass plate by William Cranch Bond, an astronomer and the first director of the Harvard College Observatory. These plates constituted a record of the sky and were vital to astronomical research at the time.

Astronomer Henry Draper used this method to create the first record of stellar spectra while photographing the star Vega in 1872. The series of lines captured on the glass plate represented components of light, which can be used to determine the star’s composition.

In 1881, Edward Pickering, frustrated with his male staff’s ability to catalog data, hired his maid, Willimina Fleming, instead. This began a long tradition of hiring women to work for him analyzing, computing and cataloging.

Cannon joined the “Harvard Computers,” also known by the unseemly name, “Pickering’s Harem,” in 1896. Her job was to study variable stars and classify them. However, it wasn’t considered proper for women to work at night, and many people felt they were too easily stressed for difficult scientific work. So, her work was primarily clerical, and she received about half the pay of her male colleagues.

In her lifetime, she was able to classify about 350,000 stars and became known as the “census taker of the sky.” Cannon was so adept at her job, she was able to analyze 200 stars per hour.

She also studied the glass plates, and the spectral lines recorded on them. While working on the project, she simplified and expanded on Harvard’s stellar classification system, which is how scientists organize stars based on their color and temperature: O, B, A, F, G, K, M. This system is still in use with only slight changes, and to this day, astronomy students are taught the mnemonic, “oh, be a fine girl (guy), kiss me!” to remember the order of spectral types.

The spectrum isn’t just a way to organize stars; it helps scientists glean essential information, like how bright a star is, and it produces light. Spectra can also be used to determine how fast a star is moving and what elements it contains. Cannon’s work in this area greatly improved astronomers’ ability to use this system effectively.

A Lasting Legacy

Some of Cannon’s incredible accomplishments are:

• Collaborating with Cecilia Payne, using data she collected to determine that stars are primarily composed of helium and hydrogen.
• Photographing the stars in the Southern Hemisphere while in Peru.
• Being the first woman to receive an honorary doctorate from Oxford University.
• Being the first woman elected as an officer of the American Astronomical Society.
• Being the first woman to win the National Academy of Sciences’ Henry Draper Medal.
• Obtaining a regular appointment as William C. Bond Astronomer from Harvard University.
• Being named the curator of Astronomical Photographs at Harvard College Observatory.

Unfortunately, despite being highly lauded, she did not receive the same consideration as her male peers. For example, she only received many of her commendations at the end of her career. She also worked for less pay than her male peers, and the spectral classification system she was primarily responsible for was named after Harvard, not her.

In spite of this, Cannon continues to serve as an inspiration for aspiring scientists everywhere. She was a pioneer for women and girls in astronomy and continues to support their efforts through the Annie Jump Cannon Award, awarded to women working toward their Ph.D. for their contribution to astronomy and related fields.

Originally publish at Medium.com.