Abell 222 is a galaxy cluster. It's located at a distance of 2.4 billion light-years from Earth.
The cluster is connected by a filament of matter to Abell 223 that is permeated by hot X-ray emitting gas. Research shows that this filament only contains about 20 percent of normal matter, the rest is assumed to be dark matter. This is seen to be in good agreement with the cosmological standard model.
References
Abell 222 Wikipedia(Text) CC BY-SA