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Oldest galaxy: Hubble telescope detects farthest, oldest galaxy yet

Oldest galaxy: Astronomers using the Hubble telescope have detected a galaxy that formed just 500 million years after the Big Bang, making it the most distant and oldest galaxy discovered so far.

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"This is an astonishing increase in such a short period, just 1 percent of the current age of the universe," co-author Garth Illingworth, of UCSC, said in a statement.

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The team also found big differences in the number of galaxies observed in the two epochs. They discovered just the one galaxy dating to 480 million years after the Big Bang, while previous searches found nearly 50 galaxies just 170 million years later.

The new observations could help astronomers better understand how the universe's first galaxies coalesced and grew, researchers said.

"We definitely see strong evidence for hierarchical buildup," Bouwens said. "It's quite striking."

Reionizing the universe

The new study also bears on an age-old question in astronomy. At about 300,000 years after the Big Bang, the hydrogen in the universe was neutral, meaning it carried no charge. By 1 billion years later, however, something had thrown off enough radiation to ionize most of this hydrogen, splitting it into its constituent electrons and protons.

"The results from this study imply that the stars and galaxies that they can detect would only provide about 12 percent of the radiation that you would need," Rachel Somerville of the Space Telescope Science Institute, who was not involved in the current study, told reporters today (Jan. 26). "So this is quite a mystery that needs to be solved."

The new results hint that early galaxies such as UDFj-39546284 may have played a role in this reionization of the universe. But their contributions alone were perhaps not great enough to do the job, suggesting that some mystery source is also partly responsible, researchers said.

The team's observations in this regard are not definitive. To get to the bottom of the reionization mystery, astronomers will need to gather more data, according to Bouwens.

"At redshift 10, we made a relatively conservative assumption about how many of these faint galaxies there were," Bouwens said. "If there actually turn out to be more, they could be more important."

Looking to the future

While the new study takes an unprecedented look into the past, new instruments will likely be required to go back even farther, to the first epochs of galaxy formation, researchers said.

One of the most promising future instruments is NASA's James Webb Space Telescope (JWST), Bouwens said. The powerful successor to Hubble, JWST has long been hampered by cost overruns and delays.

Previously slated for launch in June 2014, JWST will be able to lift off no earlier than September 2015, according to an independent review panel convened last year to assess the telescope's problems.

Whenever it's finally cleared to take to the skies, JWST will have a huge impact, according to Bouwens.

"We're now just able to scratch the surface of what will be possible," he said. "We should be able to push out to redshift 12 or 13, and maybe further. It's unclear what we'll be able to do."

You can follow senior writer Mike Wall on Twitter: @michaeldwall.

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