Astronomers using the Hubble Space Telescope announced Wednesday that they had peered through time to photograph seven galaxies that formed early in the evolution of the universe and could help explain how it formed.

The oldest galaxy dates to about 380 million years after an infinitely dense universe exploded to begin the creation of the cosmos in the Big Bang.

If the age of the oldest galaxy is validated in further observation, it will be the oldest ever found, at 13.3 billion years.

All seven galaxies are at least 13 billion years old.

They formed during a period called Cosmic Re-ionization, when light from the first stars and galaxies began breaking down dense clouds of hydrogen that formed when the universe expanded and cooled after the Big Bang, said astronomer Brant Robertson of the University of Arizona.

Robertson, the lead theorist on the Hubble Ultra Deep Field 2012 team, said the census of galaxies found in these observations indicates that the evolution of galaxies was a gradual process. As you look farther back in time, the number of galaxies decreases.

Robertson was a Hubble fellow at the California Institute of Technology when he and astronomer Richard Ellis proposed a deeper look at this previously observed region, using 100 hours on NASA's premier space telescope and its Wide Field Camera 3.

Ellis, of Caltech, said the international team of astronomers he led pushed Hubble to its limits. "This, probably, may be as deep as Hubble can look."

The observations were made in August and September in a small swath of sky first dubbed the Hubble Ultra Deep Field when it was observed in 2009.

Longer exposure and the use of an additional filter on the telescope's camera pushed observation back another 400 million years to the edge of the period when light from the first galaxies was breaking the stable hydrogen clouds of the dark, early universe into ionized particles.

"It is the period when the universe emerged from the dark ages," said John Grunsfeld, NASA associate administrator for science.

Grunsfeld, in a NASA press conference on the discoveries, said the results were particularly gratifying to him. He was an astronaut on the NASA shuttle mission that swapped an earlier camera on Hubble for the camera that took these images. He said he remembered thinking if he couldn't loosen a stuck bolt he had encountered, "we won't be able to unravel the mysteries of the universe."

Robertson said the team and other researchers will be unraveling those mysteries over time, using data gathered by Hubble to bolster or question theories about how the universe formed over its first billion years.

"We've learned there are galaxies present early in the universe and they are growing at a measured rate," he said.

The galaxies are well-developed, meaning they are not the first, he said.

There are earlier ones to be found and studied, though most of the scientists on Wednesday's NASA conference call said their discovery awaits deployment of the next-generation James Webb Space Telescope, currently scheduled for launch in 2018.

Robertson said he wouldn't rule out further discoveries by Hubble, using different techniques.

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For an illustrated thumbnail history of creation, go to the Hubble Ultra Deep Field 2012 website:

Contact reporter Tom Beal at or 573-4158.