Seoul: The age of the galaxy we are living in is around 13 billion years old, one billion years older than earlier thought, according to Korean astronomers.

They said a set of star clusters which were used to estimate the age of the galaxy and thought to be the most ancient native system were, in fact, dragged into our galaxy, the Milky Way, from a small, younger neighbor.

"It means we have to readjust the age of our galaxy. It also corroborates the theory that the Milky Way evolved through mergers and acquisitions," Yoon Suk-Jin from Yonsei University in Seoul told reporters.

The work by Yoon and his colleague Lee Young-Wook was published by last week's editions of a global journal of research, ‘Science’, and ‘New Scientist’ weekly magazine. Yoon has received a prestigious scholarship from Oxford.

Their conclusion supports results from other groups that are shaking up long-held ideas about how the Milky Way evolved, according to New Scientist magazine.

‘New Scientist’ quoted astronomer Robert Kennicutt from the University of Arizona “It’s telling us a lot about how our galaxy came together and formed,” as saying.

The Milky Way has some 150 compact assemblies of stars called globular clusters and astronomers investigate them as "astronomical fossils" to look into the past.

"We have found that we had been looking into the wrong fossils. The globular clusters which astronomers used to estimate the age of the Milky Way came from a neighboring satellite galaxy called the Large Magellanic Cloud," Yoon said.

Previous research had suggested that in the Milky Way, nearly two-dozen of the 150 compact assemblies of stars called globular clusters are actually stolen from other galaxies.

But no one had shown this for group II-b clusters- the metal-poor star systems thought to be the oldest in our galaxy, according to ‘New Scientist’.

These clusters were considered representative globular clusters that formed during the early collapse of the Milky Way.

Yoon's work showed this was not true and the clusters originated from the satellite galaxy, which appears about one billion years older than the oldest genuine globular clusters in the Milky Way.

The age difference was too small to detect through standard methods and Yoon and his colleague Lee Young-Wook used a new approach that relies on the colour of particular stars within the clusters.

The colour varies with mass, temperature and age and other factors. Yoon and Lee used computer models to create the colour distributions of specific hypothetical stars, and then matched these to the Milky Way's globular clusters.

Yoon and his colleague Lee noticed the seven globular clusters in question were in the same plane as the Large Magellanic Cloud, suggesting the satellite galaxy was the source of the merged clusters of stars used as "fossils".

"The satellite galaxy must have been circulating our galaxy before it came under tidal gravitational force from our galaxy and spilled these clusters in its track," Yoon told sources.

Kennicutt was quoted as saying by New Scientist, "I was surprised to see how these clusters are lined up in the sky."

"It's a very tantalising result," astronomer Christine Clement of the University of Toronto said. Clement added, "I think it's a starting point. We have to build other evidence."