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Globular Clusters & the Enigma of "Blue Stragglers"




Spectacular globular star cluster NGC 6362 was captured by the Wide Field Imager attached to the MPG/ESO 2.2-metre telescope at ESO's La Silla Observatory in Chile. Globular clusters are among the oldest objects in the Universe. The many yellowish stars in the cluster have already run through much of their lives and become red giant stars. But globular clusters are not static relics from the past -- some curious stellar activities are still going on in these dense star cities. This image, along with a new image of the central region from the NASA/ESA Hubble Space Telescope, provide the best view of this little-known cluster ever obtained.

NGC 6362 is home to blue stragglers -- old stars that succeed in passing for a younger age. All of the stars in a globular cluster formed from the same material at roughly the same time (typically, about 10 billion years ago for most globulars). Yet blue stragglers are bluer and more luminous -- and hence more massive -- than they should be after ten billion years of stellar evolution. Blue stars are hot and consume their fuel quickly, so if these stars had formed about ten billion years ago, then they should have fizzled out long ago. How did they survive?

Astronomers are keen to understand the secret of the youthful appearance of blue stragglers. Currently, there are two main theories: stars colliding and merging and a transfer of material between two companion stars. The basic idea behind both of these options is that the stars were not born as big as we see them today, but that they received an injection of extra material at some point during their lifetimes and this then gave them a new lease of life

This brilliant ball of stars lies in the southern constellation of Ara (The Altar). It can be easily seen in a small telescope. It was first spotted in 1826 by the Scottish astronomer James Dunlop using a 22-centimetre telescope in Australia.

The Daily Galaxy via


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