Astronomers using the world's largest ground-based telescope have discovered that galaxies started churning out stars at a high rate - when the universe was just a billion years old.For the discovery, astronomers used the world's most complex ground-based telescope array - Atacama Large Millimeter/submillimeter Array (ALMA) observatory, which was inaugurated yesterday in Chile's Atacama Desert.The discovery enables astronomers to study the earliest bursts of star formation and to deepen their understanding of how galaxies formed and evolved.Shining with the energy of over a hundred trillion suns, these newly discovered galaxies represent what the most massive galaxies in our cosmic neighbourhood looked like in their star-making youth."These aren't normal galaxies. They were forming stars at an extraordinary rate when the universe was very young-we were very surprised to find galaxies like this so early in the history of the universe," said Joaquin Vieira, a postdoctoral scholar at Caltech and leader of the study.The astronomers found dozens of these galaxies with the South Pole Telescope (SPT), a 10-meter dish in Antarctica that surveys the sky in millimeter-wavelength light-which is between radio waves and infrared on the electromagnetic spectrum.The team then took a more detailed look using the new ALMA in Chile's Atacama Desert."The new observations represent some of ALMA's most significant scientific results yet," Vieira said."We couldn't have done this without the combination of SPT and ALMA. ALMA is so sensitive, it is going to change our view of the universe in many different ways," he said.With ALMA, the astronomers found that more than 30 per cent of the starburst galaxies are from a time period just 1.5 billion years after the big bang.Previously, only nine such galaxies were known to exist, and it wasn't clear whether galaxies could produce stars at such high rates so early in cosmic history.Now, with the new discoveries, the number of such galaxies has nearly doubled, providing valuable data that will help other researchers constrain and refine theoretical models of star and galaxy formation in the early universe.But what's particularly special about the new findings, Vieira said, is that the team determined the cosmic distance to these dusty starburst galaxies by directly analysing the star-forming dust itself.

The study was published in Astrophysical Journal.