The colors and contours indicate surface brightness, and the red arrows show its estimated size. The discovery of a new and rarely seen nebula 10 billion light-years away has created a cosmic mystery: What is lighting up this dusty cloud of gases? Researchers led by Zheng Cai, a postdoctoral fellow at the University of California, Santa Cruz, have discovered an "enormous Lyman-alpha nebula," or ELAN, only the third of these vast cosmic structures ever seen.