Young building blocks of galaxies similar to the Milky Way have been spotted for the first time by astronomers, giving a tantalizing glimpse of how our stellar backyard may have formed.
The discovery of 27 "teenagers," or proto-galaxies, is further evidence that galaxies like the Milky Way were created by the clumping of smaller clouds of gas and dust, researchers reported Wednesday.
Until now, the light from these adolescent galaxies was so faint that astronomers had struggled to prove their existence. But by staring at the same patch of sky for 92 hours using some of the world's most powerful telescopes, Martin Haehnelt of Cambridge University and colleagues eventually picked out the light from 27 of the distant objects.
"We think that galaxies build up by the merging of smaller lumps. We had seen already the lumps that form bigger galaxies, but this is the first time we have seen lumps that are small enough to amalgamate into something like our galaxy," he said in an interview.
Billions of years ago the universe was filled by an extremely thin and almost uniform gas, which then started to clump together to form faint proto-galaxies, scientists believe.
Over the eons, these components came together — through mergers or collisions — to form full-fledged galaxies.
The small proto-galaxies discovered by the team from Cambridge, the Observatories of the Carnegie Institution and the Anglo-Australian Observatory are extremely distant and date from a time when the universe was only 2 billion years old.
Haehnelt said there was no guarantee of success when the team began searching an apparently empty patch of sky using the European Southern Observatory's Very Large Telescope and the Gemini Telescope in Chile, both costly resources.
"We took the largest telescope we could and stared through it for as long as we were allowed. It was a considerable risk," he said.
The team's full findings will be published next year in the Astrophysical Journal.