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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