Less dark: According to the Big Bang model, the universe developed from an extremely dense and hot state. Space itself has been expanding ever since, carrying galaxies (and all other matter) with it. The expansion means that galaxies formed immediately after the big bang are furthest away and therefore most difficult for us to see.
Credit: Wikipedia
PARIS: Astronomers have spotted galaxies which were formed just 500 million years after the Big Bang, some 250 million years earlier than the oldest galaxy observed so far.
In September 2006, Japanese astronomers announced they had 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.
Now, experts led by Daniel Stark of the California Institute of Technology in Pasadena, U.S., report in the Astrophysical Journal that they have found six galaxies with a redshift of nine, equivalent to a post-Bang birth of 500 million years.
Oldest known galaxies
The 'redshift', is a phenomenon in which the wavelength of light stretches out, appearing redder, 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.
Stark's team, which included astronomers at the Astrophysics Laboratory in Marseille, France, used the giant 10-m Keck telescope in Mauna Kea, Hawaii, over three years.
They fine-tuned 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 per cent of its current age," said French astronomer Jean-Paul Kneib.
