Astronomers have long been puzzled by two strange phenomena at the heart of our galaxy. First, the gas in the central ...

Every galaxy is thought to form at the center of a dark matter halo. Stars are formed when gravity within dark matter halos draws in gas, but astrophysicists don't know whether star-free dark matter ...

Every galaxy we can see is believed to sit at the center of a huge cloud of invisible material called a dark matter halo.