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New telescope to be named after pioneering female dark matter astronomer

Vera Rubin will be honoured for her work in observing the anomalous motion of stars.

Vera Rubin will be honoured for her work in observing the anomalous motion of stars

Vera Rubin operating a telescope at Kitt Peak National Observatory (NOAO/AURA/NSF)

New telescope named after pioneering female dark matter astronomer

A large telescope under construction in the mountains of Chile will be named the Vera C. Rubin Observatory, after the pioneering researcher who discovered evidence in galaxies for the existence of dark matter. It is also a recognition of her struggle as a woman astronomer in a field of science that was dominated by men.   

Vera Rubin's contribution to our understanding of dark matter began with observations in 1968  of the Andromeda Galaxy, a large companion to our own Milky Way. She measured the speed of the stars in the galaxy as they orbited around the galactic centre and to her surprise, she found that the stars were moving much too fast to be held by the galaxy's gravity. 

At the speed she observed, these stars should be flying off in all directions like water drops from a rotating lawn sprinkler. That meant that since they weren't flying out of the galaxy, there had to be something else — some hidden mass that was providing the extra gravity to hold the stars in place. 

The invisible mass is now known as dark matter and is believed to make up about 80 per cent of the matter in the universe. Although even today, no one knows exactly what the dark stuff is.

Dark matter map in the galaxy cluster Abell (NASA/ESA/D. Coe/JPL/CALTECH)

Rubin was not the first to come up with this idea. Thirty-five years earlier, Swiss astronomer Fritz Zwicky made a similar calculation based on observations of a group of galaxies in the Coma Cluster and postulated the existence of extra matter hidden in the group. His ideas were not widely accepted by the astronomical community because he didn't have further evidence. 

That direct evidence was provided when Rubin and her colleague Kent Ford showed how stars were moving in Andromeda Galaxy. According to Newtownian physics, the stars in the centre of a spiral galaxy should be moving faster than those on the outside. You can see this effect by watching water swirl down a drain. The water closest to the drain moves faster than the water in the rest of the sink. But Rubin observed that the stars around the outside of Andromeda were moving just as fast as those in the centre, so there had to be an invisible force at work. 

Born in 1928, Vera Rubin had an interest in astronomy since childhood, but found it difficult to pursue a career in the field because she was a woman. In fact, when she applied to Princeton University in 1948 for graduate work, she didn't get a response because back then, women were not accepted in the astronomy program. Undeterred, she attended Cornell, and then Georgetown University, where she taught for ten years.

Later, she became the first woman to use the 200-inch Hale telescope at the famous Palomar Observatory to study the large-scale motion of galaxies. That was the same instrument used by Fritz Zwicky to study the Coma Cluster. 

Then while at the Carnegie Institution in Washington, D.C., she focused on the rotation of individual galaxies such as Andromeda, which led her to the evidence for dark matter that she found in the motion of the stars. 

Throughout the rest of her career, she continued on dark matter research but also became an outspoken advocate and role model for women in science.

Vera Rubin Observatory at sunset (LSST Project/NSF/AURA)

President Bill Clinton awarded her the National Medal of Science in 1993. A ridge on Mars as well as an asteroid are named in her honour. She died in 2016 at the age of 88.

The Vera C. Rubin Observatory is a wide field telescope that will conduct the Legacy Survey of Space And Time. It will observe the entire sky at once, tracking the motions of galaxies and continuing the investigation of dark matter, which has now, thanks to Rubin's pioneering work, become its own field in astronomy.

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