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Blue Stragglers in Globular Cluster 47 Tucanae
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Blue Stragglers in Globular Cluster 47 Tucanae

February 8, 2005
The core of globular cluster 47 Tucanae is home to many blue stragglers, rejuvenated stars that glow with the blue light of young stars. A ground-based telescope image (on the left) shows the entire crowded core of 47 Tucanae, located 15,000 light-years away in the constellation Tucana. Peering into the heart of the globular cluster's bright core, the Hubble Space Telescope's Wide Field and Planetary Camera 2 separated the dense clump of stars into many individual stars (image on right). Some of these stars shine with the light of old stars; others with the blue light of blue stragglers. The yellow circles in the Hubble telescope image highlight several of the cluster's blue stragglers. Analysis for this observation centered on one massive blue straggler.

Astronomers theorize that blue stragglers are formed either by the slow merger of stars in a double-star system or by the collision of two unrelated stars. For the blue straggler in 47 Tucanae, astronomers favor the slow merger scenario.

This photo is a three-color composite of Wide Field and Planetary Camera 2 archival images taken with ultraviolet, blue, and violet filters. Green, blue, and red colors were assigned to the filters and scaled so that the red giant stars appear orange, the main sequence stars are white/green, and the blue stragglers are appropriately blue.

The ultraviolet images were taken on Oct. 25, 1995, and the blue and violet images were taken on Sept. 1, 1995.