Hubble Detects an Almost Invisible Galaxy That’s 99.9% Dark Matter

Astronomers using the Hubble Space Telescope (with Euclid and Subaru) identified CDG-2 in the Perseus Cluster, a 300-million-light-year‑away galaxy that appears almost entirely devoid of stars; the object is estimated to be 99.9% dark matter, kept together by a halo and four globular clusters after nearby galaxies stripped away its star-forming material, making it a rare, near-pristine laboratory for studying dark matter.