Hubble's views challenge star birth theory
Globular cluster NGC 2808
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Thursday, 03, May 2007 01:36
Images beamed back from the Hubble space telescope of the huge globular cluster NGC 2808 have challenged accepted views of how stars form in such clusters.
Globular clusters are gravitationally-bound groups of stars, ranging from tens of thousands to over a million stars. NGC 2808 is one of the largest of these clusters in the Milky Way.
Scientists had thought that these clusters have a single period of star birth in their early lives before experiencing a long, quiet period.
But the new Hubble images reveal that NGC 2808 has three generations of stars that formed in its early years.
Giampaolo Piotto of the University of Padua and leader of the team that made the discovery said that it was a "complete shock".
"We had never imagined that anything like this could happen," he added.
Team member Luigi Bedin of the European Space Agency commented: "The standard picture of a globular cluster is that all of its stars formed at the same time, in the same place, and from the same material, and that they have co-evolved for billions of years.
"This is the cornerstone on which much of the study of stellar populations has been built. So we were very surprised to find several distinct populations of stars in NGC 2808. All of the stars were born within 200 million years very early in the life of the 13-billion-year-old massive cluster."
Scientists behind the discovery are now attempting to work out how the cluster was able to have three star birth periods.
To do this they will be using the Very Large Telescope in Chile to make new observations of NGC 2808 and Hubble will be used to hunt for multiple generations of stars in about ten more massive globular clusters.