Giant Cosmic Cotton Ball: A Dark Matter Deficient Galaxy
The galaxy NGC 1052-DF2 resides in a field of galaxies about sixty-five million light-years away. Its low mass, only about two hundred million solar-masses, makes it a “dwarf” and its size, about fifteen thousand light-years in diameter, places it in the regime of ultra-diffuse galaxies. It is also distinguished by hosting a large population of luminous globular clusters.
Two years ago a second, similar faint dwarf galaxy was found near it, and the relative motions of these two galaxies strongly suggest they have very little or no dark matter; for comparison, in the