for National Geographic News
New images reveal a "big baby" galaxy that may lie as far from the Earth as any galaxy yet discovered. Astronomers say the new galaxy is surprisingly massive and mature for its early ageraising questions about how galaxies are formed.
"This is truly a significant object," said Richard Ellis, an astronomer at the California Institute of Technology (Caltech) in Pasadena and a member of the discovery team.
"Although we are looking back to when the universe was only 6 percent of its present age, this galaxy has already built up a mass in stars eight times that of the Milky Way."
The galaxy represents a time when the universe was just 800 million years old. Scientists place the universe's age at around 14 billion years.
The potential evidence for early star birth may shake commonly held theories of galaxy formation.
"It's telling us that star formation and the processes that led to the collapse of galaxies probably occurred at much earlier times than we thought," Ellis said.
The Birth of Galaxies
The universe's other young galaxies are generally much smaller. Scientists believe that many of these smaller galaxies gradually combined over time to build larger galaxies like the Milky Way.
But the new galaxy not only contains hundreds of billions of stars, it seems to have finished its star formation at a tender age.
"This galaxy, named HUDF-JD2, appears to have bulked up quickly, within the first few hundred million years after the big bang," said Bahram Mobasher of the Space Telescope Science Institute in Baltimore.
"It made about eight times more mass in stars than are found in our own Milky Way, and then, just as suddenly, it stopped forming new stars," he said.
No one can be sure how typical or atypical the massive young galaxy's formation might be.
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