The Dark Secret of Galaxies May Not be so Dark After All

Since the discovery of dark matter, most astronomers have concluded that every galaxy held some of its mass in the form of this enigmatic — something. Now, a pair of studies show that some galaxies do not hold onto any dark matter at all.

NGC 1052-DF2, found in 2015, is the first galaxy ever seen to contain little to no dark matter. This ultra-diffuse galaxy, which only loosely holds on to its member stars, was discovered by a team including Yale University graduate student Shany Danieli.