Scientists have discovered more than 800 "ultra dark galaxies" in the Coma Cluster.

The findings, which were made by looking at observations from the Subaru Telescope, suggest galaxy cluster are the key environment for the evolution of these types of galaxies, the National Institutes of Natural Sciences reported. The galaxies contain a extremely high levels of mysterious dark matter.

"Not only [do] these galaxies appear very diffuse, but they are very likely enveloped by something very massive," said Jin Koda, principal investigator of the study.

Many of the galaxies are similar in size to the Milky Way, but have much fewer stars. The stars that do exist are regularly subjected to strong tidal forces, suggesting something such as an excessive amount of dark matter must be protecting them. The galaxies within the cluster contain less than 1 percent visible matter (and 99 percent dark matter), which is extremely low compared to the rest of the universe.

In order for the stars to have formed, the galaxy must have lost gas during the formation process billions of years ago. It is likely the cluster environment played a key role in the loss of gas through factors such as ram-pressure stripping by intra-cluster gas and gravitational interactions with other galaxies. The dark galaxies could help shed light on model of galaxy formation.

"Follow-up spectroscopic observations in the future may reveal the history of star formation in these dark galaxies," Koda said.

In the future, the construction of Thirty Meter Telescope (TMT) by an international partnership of institutions, including the National Astronomical Observatory of Japan could allow scientists to measure the motion of the stars in detail and help solve the mystery of these dark galaxies.