Light from gas swirling around the black hole looks more like a time-lapse image of nighttime city traffic than a continuous band of material, thanks to magnetic fields threaded throughout the disk. “As the gas swirls around, it tangles the magnetic fields [and] you get these knots,” says astrophysicist Jeremy Schnittman of NASA’s Goddard Space Flight Center in Greenbelt, Md., who created the black hole images posted online September 25.