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Hello hello! Today's #scicomm thread will talk about one of the pioneers in the fields of astrophysics and cosmology aka my idol Vera Rubin, the astronomer who established the presence of dark matter in galaxies, measures spectra in the 1970s. Lets go!
Vera Rubin, (Vera Florence Cooper) was an American astronomer (1928,-2016) who made groundbreaking observations that provided evidence for the existence of a vast amount of dark matter in the universe.
As a kid, Vera was fascinated by the universe, she would track the motions of the night sky. She memorized the paths of meteors from the window of her house all night, then registered them in a notebook much to the chagrin of her mother who would tell her to "get some sleep."
Although her father was dubious about the career opportunities in astronomy, he supported her by helping her build her own telescope and going with her to amateur astronomers’ meetings. She then got a scholarship to Vassar, where she graduated as the only astro major in 1948.
Applying to graduate schools, Rubin was told that “Princeton does not accept women” in the astronomy program. Undaunted, Rubin applied to Cornell, where she studied physics under Philip Morrison, Richard Feynman, and Hans Bethe. And so, as a graduate student at Cornell
when she had to think about a topic for her master's thesis, she tried to update the old clockwork view of the cosmos for the new expanding universe, heavily supported by her husband Robert Rubin, a fellow astronomer. She reasoned that since the Earth rotated on its axis, and the
solar system rotated, and the galaxy rotated, then maybe the universe had an axis too. Maybe the whole universe rotated too. Her approach was simple. She gathered data on the 108 galaxies for which astronomers had managed to measure a redshift. Then she
separated out the motions that were due to the expansion of the universe—what astronomers call recessional motions. Did the motions that remained—the peculiar motions—exhibit a pattern? She plotted them on a sphere and thought they did. When a Cornell professor told her that
because she had a one-month-old son he would have to take her place at the Haverford AAS meeting and present this paper in his own name, she said, "Oh, I can go," and, nursing newborn and all, she went. And despite the paper being unconvincing with weak data, Rubin was undeterred
She then went on to Georgetown University, where she earned her Ph.D. in 1954. After teaching for a few years at Georgetown, she took a research position at the Carnegie Institution in Washington. Her work focused on observations of the dynamics of galaxies.
She teamed up with Kent Ford, an astronomer who had developed an extremely sensitive spectrometer. Rubin and Ford used the spectrometer to spread out the spectrum of light coming from the stars in different parts of spiral galaxies.
The stars in the disk of a galaxy move in roughly circular orbits around the center. Rubin and Ford made careful measurements of Doppler shifts across the disks of several galaxies. They could then calculate the orbital speeds of the stars in different parts of those galaxies.
When Rubin and Ford began making Doppler observations of the orbital speeds in spiral galaxies, they immediately discovered something unexpected. The stars far from the centers of galaxies, in the sparsely populated outer regions, were moving just as fast as those closer in.
It followed that there had to be a tremendous amount of unseen matter in the outer regions of galaxies where the visible stars are relatively few. Rubin and Ford went on to study some sixty spiral galaxies and always found the same thing.
“What you see in a spiral galaxy,” Rubin concluded, “is not what you get.” Her calculations showed that galaxies must contain about ten times as much “dark” mass as can be accounted for by the visible stars. In short,
at least ninety percent of the mass in galaxies, and therefore in the observable universe, is invisible and unidentified. This reminded her of Fritz Zwicky who in 1933 had analyzed the Doppler velocities of whole galaxies within the Coma cluster.
He found that the individual galaxies within the cluster are moving so fast that they would escape if the cluster were held together only by the gravity of its visible mass. Since the cluster shows no signs of flying apart, it must contain a preponderance of “dark matter”
—about ten times more than the visible matter—to bind it together. Despite his observations having being met with skeptism, here it was, in plain sight. Vera had observational evidence of Dark Matter.
Many astronomers were initially reluctant to accept this conclusion, maybe because she wasn't a seasoned astronomer or maybe because she was a woman. But the observations were so unambiguous and the interpretation so straightforward that they soon realized Rubin had to be right.
In the mid-1960s she was the first woman permitted to use the Hale Telescope at the Palomar Observatory at Caltech. Also as a recognition of her achievements, Vera Rubin was elected to the National Academy of Sciences and in 1993 was awarded the National Medal of Science.
Despite this, Rubin met with resistance during her career because of her sex, working as an academic, being a mother and an outspoken advocate for women in the sciences. Her work, although acknowledged was often snubbed because of her being a woman.
Vera died in Dec. 25, 2016 in Princeton, N.J, survived by four children.
Countless academics agree that all her work to bring the evidence of dark matter in the universe deserved the Nobel Prize but she was failed by academia yet again.
Countless academics agree that all her work to bring the evidence of dark matter in the universe deserved the Nobel Prize but she was failed by academia yet again.
Nonetheless she remains a symbol of determination, standing up for oneself and keeping that curiosity alive especially in female academics who still have to struggle to make their voices heard. Her most inspiring quote continues to keep me going, “Devise your own paths.”
