Large galaxy composed almost entirely of dark matter
DOI: 10.1063/PT.5.029682
New Scientist : Over the past few years, astronomers have spotted hundreds of large yet dim galaxies, mostly in the Coma cluster. These so-called ultra-diffuse galaxies are interesting research targets because they are extremely rich in dark matter, the nonvisible and prominent form of matter in the universe. Now Michael Beasley of the Institute of Astrophysics of the Canary Islands, Spain, and colleagues have measured the mass of an ultra-diffuse galaxy for the first time. The researchers figured out the mass of VCC 1287 in the Virgo cluster by tracking the speeds of seven globular clusters of stars orbiting the wispy galaxy. Whereas dark matter has a roughly 15:1 mass advantage over stars in the Milky Way, the ratio is 3000:1 in VCC 1287; in other words, that galaxy is made of 99.96% dark matter.