NASA’s Hubble spots nearly invisible “ghost galaxy” made of 99% dark matter

Astronomers have uncovered one of the most mysterious galaxies ever found — a dim, ghostly object called CDG-2 that is almost entirely made of dark matter. Located 300 million light-years away in the Perseus galaxy cluster, it was discovered in an unusual way: not by its stars, but by four tightly packed globular clusters acting like cosmic breadcrumbs.