... Tonight's Sky . ... Powerful cosmic-ray source found . ... They found a group of four ultra-high-energy cosmic-ray events coming from a single direction in the sky. ... With a source location tentatively pinpointed, Farrar returned to the data, checking lower energies and found a fifth event detected by HiRes in the same area of sky. ... To see what objects might be the source of the UHECRs, Farrar turned to an extensive study of thousands of galaxies, the Sloan Digital Sky Survey (SDSS). ...