They migrated here from elsewhere

Feb 23, 2010 14:01 GMT  ·  By
The Milky Way galaxy has an estimated 160 globular clusters of which one quarter are thought to be ‘alien’
   The Milky Way galaxy has an estimated 160 globular clusters of which one quarter are thought to be ‘alien’

New data from the Hubble Space Telescope appears to indicate that many stars and globular star clusters that exist in our galaxy were not born here, but arrived from elsewhere. Observations showed that these bodies were most likely generated in distant regions, and then traveled all the way to their current location. The study was conducted by astronomers at the Swinburne University of Technology in Australia, and a paper presenting it has been accepted for publication in an upcoming issue of the esteemed journal Monthly Notices of the Royal Astronomical Society, AlphaGalileo reports.

“It turns out that many of the stars and globular star clusters we see when we look into the night sky are not natives, but aliens from other galaxies. They have made their way into our galaxy over the last few billion years,” says Swinburne astronomer professor Duncan Forbes, who conducted this investigation alongside Canadian colleague, professor Terry Bridges. The two experts aimed the Hubble at globular star clusters in our galaxy, and examined their visible properties. This is the first work which accurately identified clusters that have not been born in the Milky Way.

Previous investigations had hinted at the idea that some of the clusters in our galaxy might have not originated here, but none of these “aliens” was identified until now. Clusters are large groups of stars that can contain between 10,000 and several million members. During the current research, the experts compiled the largest, high-quality database of cluster chemical properties in existence. The ages of all formations analyzed were also included in the charts. “Using this database we were able to identify key signatures in many of the globular star clusters that gave us tell-tale clues as to their external origin,” the researchers say in their paper.

“We determined that these foreign-born globular star clusters actually make up about one quarter of our Milky Way globular star cluster system. That implies tens of millions of accreted stars – those that have joined and grown our galaxy – from globular star clusters alone. We found that many of the foreign clusters originally existed within dwarf galaxies – that is ‘mini’ galaxies of up to 100 million stars that sit within our larger Milky Way. Our work shows that there are more of these accreted dwarf galaxies in our Milky Way than was thought. Astronomers had been able to confirm the existence of two accreted dwarf galaxies in our Milky Way – but our research suggests that there might be as many as six yet to be discovered,” Forbes says.

“Although the dwarf galaxies are broken-up and their stars assimilated into the Milky Way, the globular star clusters of the dwarf galaxy remain intact and survive the accretion process. This will have to be explored further, but it is a very exciting prospect that will help us to better understand the history of our own galaxy,” the expert concludes.