Billions of years ago the universe was a star-forming machine. Some galaxies were churning out a star every few hours. But today the Milky Way produces maybe a couple of stars annually. Now a study shows that the busy period of star formation was in full swing earlier than had been thought.

Researchers used an observatory still being built to examine dozens of so-called starburst galaxies billions of light-years away. The 66 linked dishes of the ALMA telescope array in Chile were inaugurated on March 13. But even a beta version with 16 dishes was able to peer deep into the history of the universe.

ALMA measured precise redshifts, or cosmic distances, to 18 of the starburst galaxies. Ten of those turned out to have redshifts greater than 4, meaning that the light from the galaxies took more than 12 billion years to reach us. The study is in the journal Nature. [Joaquin D. Vieira et al., Dusty starburst galaxies in the early Universe as revealed by gravitational lensing]

On average the starbursts were much farther away than similar, previously known objects. So the new study shows that vigorous bursts of star formation were already happening just a billion years after the Big Bang. Proving that our universe was a precocious youth.

—John Matson

[The above text is a transcript of this podcast.]

[Scientific American is part of Nature Publishing Group.]

