A strange discovery that challenges how galaxies form

Astrophysicist and science journalist Maria Luísa Buzzo discusses galaxies that appear to contain little or no dark matter, challenging long-held theories of how galaxies form. Drawing from her Scientific American reporting, she explains how these unusual dwarf and ultradiffuse systems may have formed, including the “bullet dwarf” scenario where cosmic collisions strip away dark matter. The discovery is prompting scientists to rethink existing models and underscores how much remains unknown about the universe’s structure.