Thirteen billion years old ultra-blue galaxies, which were formed around 700 million years after the Big Bang, have been discovered by astronomers, US space agency NASA has said.<br/>Using NASA's Hubble Space Telescope, astronomers from University of California have broken the distance limit for galaxies by uncovering the primordial population of compact and ultra-blue galaxies that were never seen before.<br/>These newly-found galaxies are crucial to understand the link between the birth of the first stars, the formation of the first galaxies and the sequence of evolutionary events<br/>that resulted in the assembly of Milky Way and other "mature" elliptical and majestic spiral galaxies in today's universe. <br/>The Hubble Ultra Deep Field 2009 (HUDF09) team combined the new Hubble data with observations from NASA's Spitzer Space Telescope to estimate the ages and masses of these primordial galaxies.<br/>"The masses are just 1 per cent of those of the Milky Way," explained team member Ivo Labbe of the Carnegie Observatories.<br/>He further noted that "to our surprise, the results show that these galaxies existed at 700 million years after the Big Bang and must have started forming stars hundreds of millions<br/>of years earlier, pushing back the time of the earliest star formation in the universe." <br/>