Webb spots runaway black holes carving stellar contrails across galaxies

James Webb Space Telescope observations provide strong evidence for runaway black holes being kicked through galaxies by gravitational-wave recoil, leaving long wakes of star formation (contrails) in their path. Webb images show supermassive black holes of millions of solar masses traveling at hundreds to roughly a thousand kilometers per second, producing straight trails that can extend tens to hundreds of thousands of light-years. The phenomenon fits with theories of rotating black holes releasing spin energy and with gravitational-wave mergers, and while such runaways could theoretically traverse between galaxies, their occurrence in our region would be exceedingly rare. The discovery adds a striking new chapter to our understanding of the universe.