This is the galaxy nicknamed “DF2”. Found some 60 million light-years from Earth, this galaxy has scientists baffled as it doesn’t have dark matter.
Because DF2 would be the very first known galaxy without the mysterious substance, the news of its discovery in 2018 quickly spread throughout the astronomical community. If confirmed, a galaxy without dark matter would throw a wrench into our understanding of how galaxies form and evolve. Every galaxy we know of so far has a sizeable chunk of the invisible matter, so finding one without it would mean one of two things: Either DF2 never had any dark matter to begin with, or it somehow managed to shed its dark matter during the course of its life.
Astronomers have different theories about the galaxy. Check them out on Discover.
(Image Credit: NASA/ESA/P. van Dokkum (Yale University))