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Pioneering Women

How Annie Jump Cannon Cataloged The Stars

"A life spent in the routine of science need not destroy the attractive human element of a woman's nature."

So said astronomer Annie Jump Cannon, nicknamed the "Census Taker of the Sky," who was known for her work classifying the stars.

Shoot For The Stars

You might have heard the expression: "Oh! Be A Fine Girl/Guy – Kiss Me!" It's an easy pneumonic device to remember the ranking system of the stars, and we have Annie Jump Cannon to thank for it. While working as a computer at Harvard in the 1890s, Cannon came up with what is now called the Harvard system of stellar classification, ranking stars as O, B, A, F, G, K or M. "Cannon simplified two earlier schemes into one that astronomers still use today. Her classification had just seven letters arranged by decreasing temperature: OBAFGKM," according to Air and Space Smithsonian. "Over the course of her life, Cannon classified the spectra of over 350,000 stars—legend has it that she could look at any stellar spectra and classify it in just three seconds."

Annie Jump Cannon at her desk at the Harvard College Observatory.

Cannon's astronomy career lasted nearly 40 years. She retired in 1940, a year before her death at age 77. To this day she is a legend among astronomers and the namesake of the Annie Jump Canon awarded "each year by the American Astronomical Society, goes to "a North American female astronomer within five years of receiving her PhD."

Star Classification - Sixty Symbols

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Key Facts In This Video

  1. Originally, stars were classified based on a brightness rating, with one being very bright and 5 being very dim. 01:01

  2. Temperature is one of the most important properties to consider when classifying. 04:13

  3. The Earth's sun ranges right in the middle of temperature, mass and brightness when compared to other stars we know of. 06:07

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