An international team of astronomers has found the oldest black holes ever observed, in a discovery that provides clues to the formation of the early universe, dpa reported today. The black holes are 13 billion light years from Earth, meaning astronomers are observing what they were like just 1 billion years after the formation of the universe, scientists said Wednesday. Using the orbiting Chandra X-Ray Observatory, astronomers took images of a portion of the sky and used x-rays to find the black holes that were hidden at the centre of their galaxies. The observations show that the black holes grow in tandem with their galaxies, sucking in gasses and other material that makes the black holes even more massive. At least 30 per cent of the galaxies in the early universe contained these kind of super-large black holes at their centres, said Ezequiel Treister of the University of Hawaii. "What we've seen are baby black holes in galaxies at dawn of the universe," said Kevin Schawinski, a Yale University scientist. He said the black holes are still taking in material and will continue to grow. The data, which was published in the journal Nature, shows that extremely massive black holes existed in the early universe and that they either began big or grew very rapidly, said scientist Priyamvada Natarajan of Yale.