The Universe still produces massive newborn galaxies full of baby stars, despite being billions of years old.
Typical young galaxies brim with newborn stars and exploding supernovas
The findings are a surprise - many astronomers thought the Universe had gone through a "cosmic menopause" and was now incapable of such formations.
The Galaxy Evolution Explorer (Galex) telescope detected 36 bright, compact galaxies resembling the youthful ones that existed billions years ago.
These "new" galaxies, though, may be as young as 100 million years old, as viewed from Earth.
By comparison, the Milky Way, our galaxy, is approximately 10 billion years old.
The new galaxies are relatively close to us, ranging from two to four billion light-years away.
The US space agency (Nasa) launched its $100m Galex telescope on 28 April 2003 to look for newborn star systems in the distant, early cosmos. The latest findings come from its first sweep of the skies.
"We knew there were really massive young galaxies aeons ago, but we thought they had all matured into older ones more like our Milky Way," said Dr Chris Martin, principal investigator for Galex at the California Institute of Technology (Caltech) in Pasadena, US.
"If these galaxies are indeed newly formed, then this implies parts of the Universe are still hotbeds of galaxy birth."
Astronomers believe the Universe unfolded after the Big Bang more than 13 billion years ago.
As the expanding Universe cooled, it absorbed hydrogen and helium. These elements collapsed under gravity to create the first stars and galaxies.
Galex has conducted its first sweep to look for new star systems
When the Universe was young, massive galaxies were regularly bursting into existence. But this activity was thought to have peaked eight to 10 billion years ago.
Over time, fewer and fewer galactic progeny were born and the early generation galaxies matured into ones that look like our own. Until now, astronomers thought they had seen the last of the giant babies.
'Alive and well'
The new discovery offers astronomers their first close-up glimpse at what the Milky Way might have looked like in its infancy.
"Now we can study the ancestors to galaxies much like our Milky Way in much more detail than ever before," said co-author Dr Tim Heckman of Johns Hopkins University in Baltimore, US.
"It's like finding a living fossil in your own backyard. We thought this type of galaxy had gone extinct, but in fact newborn galaxies are alive and well in the Universe," he added.
The results will be published in an upcoming issue of the Astrophysical Journal.