NASA says a small telescope on one of its spacecraft has made a big discovery, an example of a galaxy cluster, one of the rarest and largest galaxy groupings. The Wide-field Infrared Survey Explorer has detected one of the massive structures -- a collection of thousands of galaxies bound together by gravity -- NASA\'s Jet Propulsion Laboratory in Pasadena, Calif., reported Thursday. Such galaxy clusters were created out of seeds of matter formed very early in the universe, and grew rapidly in a phenomenon dubbed inflation, astronomers said. \"One of the key questions in cosmology is how did the first bumps and wiggles in the distribution of matter in our universe rapidly evolve into the massive structures of galaxies we see today,\" said Anthony Gonzalez of University of Florida, Gainesville, who led the research program using the WISE data. \"By uncovering the most massive of galaxy clusters billions of light-years away with WISE, we can test theories of the universe\'s early inflation period.\" The first cluster spotted, MOO J2342.0+1301, is more than 7 billion light-years away, which means astronomers are seeing it as it existed halfway back to the time of the big bang. It is hundreds of times more massive than our Milky Way, they said.