14. Dark Matter Galaxies
Some of the universe’s strangest residents are the so-called dark matter galaxies, like Dragonfly 44. These “ghost galaxies” appear faint but are astonishingly massive—composed almost entirely of mysterious dark matter rather than stars. Their elusive, nearly invisible nature complicates efforts to study them, challenging astronomers to rethink how galaxies form and evolve. Discoveries like these highlight how much remains unknown about the cosmos. Source: Yale News