Astronomers in Europe and the United States said on Wednesday they had spotted the oldest galaxy ever found, a star cluster 13.2 billion light years away.

Light reaching Earth today from galaxy MACS 1149-JD is truly ancient, they reported in the British journal Nature.

The rays were sent out 490 million years after the Big Bang that created the Universe some 13.7 billion years ago.

"We estimate that it (the galaxy) formed less than 200 million years after the Big Bang," the team said.

Until now, researchers have found more than 100 galaxies believed to have formed between 650 and 850 million years after the birth of the cosmos.

But only one, reported last year, has been found that can be dated with confidence back to 500 million years.

Detection of MACS 1149-JD is a breakthrough for a new technique in astronomy, for galaxies that are so distant they have a brightness weaker than a candle on the Moon.

In this case, the astronomers used a phenomenon called a gravitational lens to snatch the light.

Galaxies that are grouped together in a tiny arc of the sky contain large amounts of "dark matter," an enigmatic substance that can only be perceived indirectly, through its gravitational effect on light.

Closely-gathered galaxies results in dark matter bundling light together, thus making it brighter and easier to detect.

The astronomers searched for old, distant galaxies lurking behind more recent galaxies.

The study, using NASA's orbiting Hubble and Spitzer telescopes, was led by Wei Zheng at Johns Hopkins University in Baltimore, Maryland.