Dr. Vera Rubin is a giant of astronomy whose work appears in every modern textbook. She has helped to build the foundation on which observational cosmology is based. This article helps to explain some of her paradigm-shifting discoveries.
In the 1970s Dr. Rubin starting taking spectra of stars at various distances from the Galaxy’s center. From each spectrum, which is just the light from a star dispersed into its rainbow of color, she measured their speeds. Surprisingly, she and found that all stars in the Milky Way move at the same speed! How could this be?
Her explanation is one that we still hold as true today. She says that the reason for stars all to have the same speed is that there is a significant amount of extra matter in the Galaxy that we do not see. We now call this extra matter dark matter.
She further found that there is not just a little bit of dark matter but a huge amount of it. In fact there is about ten times more dark matter than the visible matter that you and I and the stars are made out of.
Who is this person who helped to change the way we think of the universe? To find out, I consulted various textbooks, and somewhat surprisingly could not find her name. Fortunately, she wrote an excellent book called ‘Bright Galaxies, Dark Matters,” and it is from this book that we are privy to hearing a bit of her story.
Dr. Rubin was born in 1928 and earned her degrees from the few places in the U. S. that were accepting female physics students. Her B. S. degree is from Vassar College, her M. S. degree is from Cornell University, and her Ph. D. is from Georgetown University (Jesuit).
After earning her degree, she stayed on at Georgetown teaching for a few years, and then moved on to Carnegie Observatories to continue to do much of her fundamental work in the field of observational cosmology. She did all this while bearing and raising 4 children, each of whom grew up also to earn Ph. D.’s.
Her discovery of dark matter in the Milky Way is as puzzling to answer today as it was in the 1970s. Dr. Rubin sums this all up best with, “In a spiral galaxy, the ratio of dark-to-light matter is about a factor of ten. That’s probably a good number for the ratio of our ignorance-to-knowledge. We’re out of kindergarten, but only in about third grade.”