dipper@utastro.UUCP (Debbie Byrd) (12/11/85)
This is the anniversary of the birth of a great woman astronomer. More on Annie Jump Cannon -- when we come back. December 11 Annie Jump Cannon On today's date in the year 1863, a girl was born in Delaware who later became one of this country's greatest astronomers. Annie Jump Cannon joined the staff at Harvard College Observatory in 1896. She discovered five novae, and more than three hundred variable stars. But by far her most important work was in classifying stars according to the rainbow-like array of colors known as a star's spectrum. The spectrum of a star is obtained by splitting light from that star into its component colors -- something like what you can do yourself with sunlight by letting it shine through a prism. The spectra of stars are powerful tools in astronomy. They're often said to be like fingerprints -- with each spectrum revealing information about the identity of the star. In general, stars are classified in a variety of catagories, from hot blue stars to cool red ones. The differences in their spectra are due partly to temperature -- and partly to the individual chemical compositions of the stars. That's why stellar spectra are so useful. They tell us what stars are made of. Annie Jump Cannon examined and classified spectra from a vast number of stars. The catalog that resulted from her work included the classification of spectra for more than 250 thousand stars. That basic system -- developed around the beginning of the 20th century by Annie Cannon and others at the Harvard College Observatory -- is the fundamental system of stellar classification still in use today. Script by Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin