If the discovery of 47 so-called “ultra-dark” galaxies was considered “a lot,” scientists will have to come up with a new descriptor for their latest find: Astronomers from Stoney Brook University and the National Astronomical Observatory of Japan (NAOJ) announced the discovery of a whopping 854 ultra-dark galaxies in the Coma Cluster, suggesting that clustering definitely has something to do with the way these galaxies form, grow and evolve.
“The findings suggests that these galaxies appear very diffuse and are very likely enveloped by something very massive,” said Jin Koda, PhD, principal investigator of the study and Associate Professor in the Department of Physics and Astronomy at Stony Brook University.
The galaxies are about the same size as our own Milky Way, but differ in one key area: They have only about 0.1% the number of stars that ours does (hence the “dark” moniker). With so few stars, astronomers would expect galaxies of this size to be held together very loosely and subject to diffusion, yet they’re not. Instead, the scientists believe that dark matter may be responsible for holding them together.
“This discovery of dark galaxies may be the tip of the iceberg,” said Dr. Koda. “We may find more if we look for fainter galaxies embedded in a large amount of dark matter, with the Subaru Telescope and additional observations may expose this hidden side of the Universe.”
Scientists aren’t quite sure how the galaxies lost the gasses created to produce new stars. Theories include am-pressure stripping by intra-cluster gas, gravitational interactions with other galaxies within the cluster, and gas outflows due to simultaneous supernova explosions triggered by the ram pressure or gravitational encounters.
But, really, because dark matter is so poorly understood, theories are all we have. Until stronger telescopes and better technology can reach these parts of the universe, dark matter will remain mostly a mystery.