“Dark galaxies,” as the name suggests, are made primarily of dark matter. And, given the elusive nature of this exotic matter that constitutes nearly 27 percent of the entire universe, they have been extremely hard to detect.
Now, a team of researchers from the Stony Brook University in New York and the National Astronomical Observatory of Japan have discovered 854 “ultra-dark galaxies” -- containing only one-thousandth of the stars present in the Milky Way -- in the Coma cluster, located over 320 million light-years from Earth. The discovery, made using the Subaru Telescope at the Mauna Kea Observatory in Hawaii, indicates that these galaxies are dark because, during their formation process billions of years ago, they lost the gas needed to create new stars.
“The findings suggest that these galaxies appear very diffuse and are very likely enveloped by something very massive. … We believe that something invisible must be protecting the fragile star systems of these galaxies, something with a high mass,” Jin Koda, principal investigator of the study and associate professor in the department of physics and astronomy at the university, said, in a statement released Monday.