Ghostly galaxies composed almost entirely of dark matter speckle the universe. Unlike normal galaxies, these extreme systems contain very few stars and are almost devoid of gas. Most of the luminous matter, so common in most galaxies, has been stripped away, leaving behind a dark matter shadow. These intriguing galaxies—known as dwarf spheroidals—are so faint that, although researchers believe they exist throughout the universe, only those relatively close to Earth have ever been observed. And until recently, no scientific model proposed to unravel their origin could simultaneously explain their exceptional dark matter content and their penchant for existing only in close proximity to much larger galaxies.

Now, Stelios Kazantzidis, a researcher at Stanford University's Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), in collaboration with ... has developed an elegant explanation for how galaxies come to be dominated by dark matter. ...   more »