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More to Light Than Meets the Eye
Science >
You have probably seen a rainbow of light splash on a wall as the sun shines through a piece of cut glass or crystal. What is that light? What is it revealing about our sun, or even about our universe?
A curious girl with the curious name of Annie Jump Cannon asked those questions over a century ago. Her marvel about light and her fascination with the stars led her to become one of the premier women of astronomy of the entire 20th century.
Light from a source can be passed through a prism and spread out into its spectrum. We see the sun's light dispersed like this when we marvel at the rainbow. With the proper equipment one can see thin dark lines in the spectrum, telltale lines which reveal the presence of different elements at the light source. Thus, and amazingly, the composition of a star hundreds of trillions of miles away can be determined merely by examining its light.
In the late 1800's taking the spectra of stars was becoming the thing to do. But it was tedious and in great need of being organized.
One such lab that was willing to take on that daunting task was Harvard College Observatory. There, Edward Pickering worked for decades to give the world the classic Henry Draper Catalog with hundreds of thousands of stellar spectra. But that's only part of the story.
Pickering hired women to be used as "computers" to catalog the flood of spectra coming into the observatory. Although most of the women toiled for a while, then left in obscurity, some of them toughed it out and tried to make sense of all the colorful information flowing their way.
One of his computers was Annie Jump Cannon.
Blessed with a father who felt it was important for his daughter to get an education, Annie Cannon graduated from Wellesley in 1884, then shortly after joined Pickering and his computers at Harvard. And there she stayed --- for 42 years.
In those decades of patience and persistence she personally managed to catalog over 400,000 spectra! And in doing so helped give us the Henry Draper Catalog that astronomers use to this day.
But what most all astronomy students know her for is her classification system. In examining all those spectra she managed to see repeating characteristics of spectra which helped turn a then convoluted and confusing classification system into the modern one.
She gave us the famous sequence --- OBAFGKM. The hottest, meanest, bluest, biggest stars are the O's. As we proceed through the letters we get stars that are cooler, smaller, less energetic. Our own star is a G star. The cool red ones are the K's and M's. Even today astronomy students memorize the sequence with the mnemonic, Oh Be A Fine Girl (Guy), Kiss Me!
Her work and the work of her fellow computers helped us to see the big picture of stars and star formation. And all this was accomplished before the advent of modern computers.
Amazingly, although she was internationally recognized for her efforts, her name did not appear in the Harvard catalog, and she was not even officially acknowledged by Harvard until she was 75 years old, three years before her death.
Wrote Miss Cannon, "Classifying the stars has helped materially in all studies of the structure of the universe. No greater problem is presented to the human mind. Teaching man his relatively small sphere in the creation, it also encourages him by its lessons of the unity of Nature and shows him that his power of comprehension allies him with the great intelligence over-reaching all."
Questions or suggestions? Write Mark Ritter here.
Posted by Administrator at 2002.10.12 02:25 PM | Comments (0)
