PHOTO CAPTION:

FOR RELEASE:  October 29, 1997

PHOTO NO.:  STScI-PRC97-35

BLUE STRAGGLERS IN GLOBULAR CLUSTER 47 TUCANAE

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 image is a 3-color composite of archival Hubble Wide
Field and Planetary Camera 2 images in the ultraviolet (blue),
blue (green), and violet (red) filters.  Color tables were 
assigned and scaled so that the red giant stars appear orange,
main-sequence stars are white/green, and 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.

Credit:  Rex Saffer (Villanova University) and Dave Zurek (STScI), 
and NASA