This dark galaxy, named Dragonfly 44, was first detected in 2015, through the use of the Dragonfly Telephoto Array in New Mexico. With a combination of eight telephoto lenses and cameras, the array is designed to look at objects in space that aren’t bright enough to see with other telescopes. While it’s as big as the Milky Way, it only emits about 1 percent as much light.
Dragonfly 44: a galaxy that big couldn’t possibly hold itself together with so few stars. There wouldn’t be enough gravity, and the stars would drift apart. They suspected that dark matter was responsible for holding the galaxy together, and this particular galaxy seemed like it contained a ton of it, so they set out to determine exactly how much.
— source scientificamerican.com | 2016