Universe's 'dark ages' shorter than thought

12th July 2007, Comments 0 comments

PARIS, July 12, 2007 (AFP) - Astronomers in the United States and France said Wednesday they had spotted galaxies which were formed just 500 million years after the "Big Bang" that created the Universe, some 250 million years earlier than the oldest galaxy observed so far.

PARIS, July 12, 2007 (AFP) - Astronomers in the United States and France said Wednesday they had spotted galaxies which were formed just 500 million years after the "Big Bang" that created the Universe, some 250 million years earlier than the oldest galaxy observed so far.

Their technique is based on so-called redshift, a phenomenon in which the wavelength of light stretches out as its source recedes.

As the Universe has never stopped expanding since the Big Bang some 13.7 billion years ago, the theory is that the "redder" the light, the farther -- and older -- its source.

Last September, a team led by Japanese astronomer Masanori Iye said it found a galaxy with a redshift of seven, suggesting that the star cluster formed around 12.7 billion years ago, or 750 million years after the Big Bang.

Reporting in the US publication Astrophysical Journal, watchers led by Daniel Stark of the California Institute of Technology (Caltech), say they found six galaxies with a redshift of nine, equivalent to a post-Bang birth of 500 million years.

The team, which included astronomers at the Astrophysics Laboratory in Marseille, southern France, used the giant 10-metre (32.5-feet) Keck telescope in Mauna Kea, Hawaii, over three years.

They finetuned the search by exploiting a phenomenon called gravitational lensing.

Under this, the gravitational force of nearby galaxies bends and focuses the light from more distant clusters.

"We identified six youthful galaxies that were actively forming stars and were located at a distance corresponding to the time when the universe was only 500 million years old, or less than four percent of its current age," said French astronomer Jean-Paul Kneib.


Copyright AFP

Subject: French news

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