Fifteen massive galaxies may have formed relatively recently despite wide-held belief they formed 13 billion years ago, UPI quoted a U.S. astronomer as saying. The relatively low abundance of heavy elements suggests the 15 galaxies may be 3 billion or 4 billion years old, said John Salzer, an astronomer at Indiana University who led a team in studying the galaxies. Most theories of galaxy formation have held that such massive, luminous systems, including the Milky Way, formed shortly after the big bang 13 billion years ago, he said. If the team's new theory is correct, astronomers could use the 15 galaxies to study to stellar formation and evolution, the university said in a release. The discoveries are the result of a several-year survey of more than 2,400 star-forming galaxies, Salzer said, noting previous surveys failed to find the unusual galaxies.