AST 104 Lecture Notes - Lecture 7: Annie Jump Cannon, Harvard College Observatory, Harvard Computers
Document Summary
The harvard computers, late 1880s worked to classify almost one million stellar spectra collected by the harvard college observatory. Nonetheless classified countless stars into the seven spectral classes and solved the mystery of their nature. So skilled she could classify several hundred spectra per hour. Stars of type a couldn"t be at the beginning of a sequence, because there were two different kinds of spectra that were almost like a stars. B stars have pretty strong hydrogen lines, plus helium lines. F stars also have pretty strong hydrogen lines, plus calcium lines. (so, a stars had to be in the middle of the sequence!) The darkest hydrogen absorption lines will be produced by stars with intermediate temperatures. The order that cannon and the harvard computers identified is based on increasing temperature. Each spectral class is divided into 10 subclasses (0 through 9). So, the history is reflected in the order of spectral classes: o, b, a, f, g, k, m.
