APOD: 2021 September 18 - Rubin's Galaxy

Good afternoon, Rallypoint. Today's Astronomy Picture of the Day (APOD) is titled "Rubin's Galaxy." Found in the constellation Perseus, Rubin's Galaxy (aka UGC 2885) lies about 232 million light years from Earth. It is named after Vera Florence Cooper Rubin (d. 2016), an American astronomer who pioneered work on galaxy rotation rates. Her research (which included UGC 2885) showed that spiral galaxies rotate so quickly that the gravity of their constituent stars was insufficient to keep them from flying apart. Because they stay intact, a large amount of unseen mass must be holding them together. This became known as "the galaxy rotation problem."

The supporting calculations for "the galaxy rotation problem" showed that galaxies must contain at least five to ten times as much 'dark' matter as ordinary, visible matter. Her work became the first persuasive results supporting the theory of dark matter, initially proposed by Fritz Zwicky in the 1930s. This data has subsequently been confirmed through radio astronomy, the discovery of the cosmic microwave background, and images of gravitational lensing similar to those featured on previous APODs.

Both Vera Rubin Ridge (on Mars) and Asteroid 5726 Rubin are named in her honor. The National Science Foundation's Vera C. Rubin Observatory is located on a mountain in Cerro Pachon, Chile and focuses on the study of dark matter and dark energy.