Astronomers, through their study of the Hubble Space Telescope and data from other observatories, discovered a faint, nearly undetectable galaxy that exists as a dark matter-dominated celestial body. The object called Candidate Dark Galaxy-2 or CDG-2 is located about 300 million light-years from Earth in the Perseus Cluster.
The researchers from the University of Toronto and other institutions published their findings in The Astrophysical Journal Letters. The researchers discovered the galaxy through their study of globular clusters and their gravitational effects, providing new evidence about dark matter systems and cosmic evolution.
Scientists say that CDG-2 is 99.9% dark matter. Dark matter exists in an invisible state that humans cannot see, but it creates gravitational forces that determine how galaxies and the universe become structured. The substance occurs in quantities that exceed ordinary matter by a factor of five.
Postdoctoral researcher Dayi Li of the University of Toronto classified the object as a “near-dark galaxy.” He said CDG-2 occurs at the highest level of galaxies with low surface brightness because it shows no visible stars. The Milky Way has a brightness level 20,000 times higher than its brightness level.
How did scientists find CDG-2?
Researchers used data from the Hubble Space Telescope, the European Space Agency’s Euclid Observatory and the Subaru Telescope in Hawaii. The researchers used globular clusters, which form tight groups of old stars, as their search target instead of hydrogen gas as their search target. The researchers found four clusters that appeared with a faint halo that indicated a hidden galaxy.
Scientists believe larger galaxies took away the gas CDG-2 needed to create new stars, leaving behind only the dark matter halo and some clusters.
