Perseus Cluster

In the low-luminosity galaxy CDG-2, within the dashed red circle on the right, dark matter is dominant and contains only a sparse scattering of stars. Left: The full Hubble image. Credit: NASA, ESA, Dayi Li (UToronto); Image Processing: Joseph DePasquale (STScI)

A "ghost galaxy" composed of 99% dark matter has been discovered 300 million light-years away

Astronomers identified the galaxy CDG-2 in the Perseus cluster using only four globular clusters and observations from the Hubble and Euclid Space Telescopes and the Subroutine Observatory in Hawaii.