The first bright galaxies in the universe apparently formed very rapidly, jumping from just one or so in number to hundreds in the span of little over 1 percent of the universe's age, astronomers find.

Using either the Hubble Space Telescope or the Subaru telescope on Hawaii, one of the world's largest ground telescopes, two independent teams of astronomers scanned the skies for the faint light emitted roughly 13 billion years ago by stars in the most distant visible galaxies. The universe is roughly 13.7 billion years old.

Scientists can discern the age and distance of a galaxy by looking at how much light from it has shifted toward the red end of the spectrum. This redshift measures how the expansion of the universe since the Big Bang has stretched the wavelengths of light before it has reached us.

Astronomers Garth Illingworth and Rychard Bouwens at the University of California at Santa Cruz discovered 500 or so bright galaxies around 900 million years after the Big Bang. But just 200 million years earlier, they and a team led by astronomer Masanori Iye at the National Astronomical Observatory in Tokyo could only confirm the presence of one such galaxy, with maybe a few more candidates.

"That suggests evidence for how dramatically things changed," Illingworth told "It was a pretty vibrant period in the life of the universe."

Investigating when and how the first galaxies were formed helps shed light on when stars first forged the heavier elements, such as the ones that planets and people are made out of, Illingworth said.

These bright galaxies likely built up over time as smaller galaxies not detectable by current telescopes collided and merged. Getting a better picture of galaxy formation will have to wait for more advanced telescopes, such as the James Webb Space Telescope, due to launch in 2013.

"We are at the very limits of the current technology at probing the most distant galaxies," Iye said.

Both teams of scientists reported their findings in the Aug. 14 issue of the journal Nature.

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