Young Stars In Old Cluster Challenging Understanding Of Cosmic Evolution

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Astronomers have discovered young stars in an old cluster in our neighborhood – Large Magellanic Cloud. Where is the catch perhaps you wonder? In the core of our understanding of cosmic and stellar evolution. New observations and study challenge it.

Stars Evolution

To see how this finding messed up with our current knowledge of stellar evolution we have to back on its formation. As an example, we can take Milky Way clusters. Star clusters, which are the group of stars bounded by gravity, contains the stars made of the same cloud of molecular gas formed at roughly the same time. So each cluster has its own same aged stars. That is what every previous observation have shown and based on that the model of stellar evolution is built.

Typical star cluster M4 which is one of the largest globular star clusters in our galaxy containing over 10,000 stars

Now astronomers confront with an unexpected situation. Scientists from the University of Western Australia used Spitzer telescope and thanks to its infrared wavelengths they managed to capture 15 very young stars comparing to other ones in our third closest galaxy Large Magellanic Cloud. To be weirder, 7 of them are located in the center of the cluster. Scientists are now confused and not sure how to explain this. Firstly they thought that these stars are formed from molecular gas leaking into the cluster from interstellar space. However, after radio telescope observations it is eliminated due the lack of correlation between interstellar hydrogen gas and the location of the clusters astronomers were studying.

The circles represent clusters that contain at least one star being formed hundred of millions of years after the rest. Image credit: Space Telescope Science Institute/AURA/NASA

Dr. Bi-Qing For, from the International Centre for Radio Astronomy Research in Perth, believes that these younger stars have actually been created out of the matter ejected from older stars as they die. This would mean researchers have discovered multiple generations of stars belonging to the same cluster.

This isn’t the first time that classic model of stellar evolution is put to the test. Back in 2007, Hubble Space Telescope discovered a large number of stars in the same galaxy, that have diverse characteristics. Australian team hopes that Hubble will be pointed to the studied clusters and allows that to finally confirmed that is possible that star clusters can contain several generations of stars.

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Debbie Quinn
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Interesting. A new challenge.