Astronomers peering into deep space believe that the first big galaxies in the universe were forged around 700-million years after the Big Bang that initiated the cosmos.
In a record-breaking scan of the skies, a team led by Japanese astronomer Masanori Iye found a galaxy whose light has taken 12,7-thousand million years to reach Earth.
The galaxy must have formed when the universe was only 750-million years old, according to their study, which appears on Thursday in Nature, the British weekly science journal.
It is the oldest galaxy whose age has been spectroscopically confirmed.
Under this, astronomers analyse the so-called ”redshift” of stars. The universe is expanding because of the Big Bang, and the light from receding objects moves towards longer, redder wavelengths. The older an object is, the greater its redness.
In a separate study, also published in Nature, University of California at Santa Cruz astronomers Rychard Bouwens and Garth Illingworth used the orbiting Hubble telescope to explore the formations of galaxies in the early Universe.
They found hundreds of galaxies at redshifts around 900-million years after the Big Bang.
But when they looked at higher redshifts, at about 700-million years after the Big Bang, they found unconfirmed evidence for only one galaxy, when they had expected to find many more.
This backs theories about a ”hierarchical” formation of big galaxies — that these huge clusters were built up over time as smaller galaxies collided and merged, they believe.
”The bigger, more luminous galaxies were just not in place at 700-million years after the Big Bang,” said Illingworth.
”Yet 200-million years later, there were many more of them, so there must have been a lot of merging of smaller galaxies during that time.”
A paper published last November by astronomers in the United States estimated that the first stars were born when the universe was around 100-million years old.
Dating the first stars and galaxies is important. These bodies were fuelled by hydrogen, the lightest and simplest element, that came after the Big Bang, which occurred around 13-billion years or so ago.
In turn, they crunched out heavier elements such as carbon, nitrogen and oxygen that eventually became the basis of life. – Sapa-AFP