Dr. Vera Rubin and her collaborator, Dr. Kent Ford, used a device called a spectrometer. The spectrometer allowed them to measure how fast stars in a galaxy were moving.
Spectrometers can also be used to determine which atoms are present in a star. Astronomer Annie Jump Cannon figured out a way to classify stars based on their unique spectral fingerprint.
Visit the STEM Learning website to build your own spectrometer and explore how light can be split into all the colors of the rainbow and give us clues about the motion and makeup of stars.