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foc47tuc.txt
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1996-01-12
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HUBBLE UNCOVERS FAINT STARS IN THE CORE OF GLOBULAR CLUSTER 47 TUCANE
These comparison images of the core of the globular cluster 47
Tucanae (NGC104) were taken with the COSTAR-corrected Faint
Object Camera to show the improvement in performance when
compared to images taken with the uncorrected camera.
(left)
The pre-COSTAR image was taken on 27 October 1993 using the F/96
mode. Even prior to the servicing mission this was considered an
impressive HST image. The star density is high and none of the
stars are bright enough to show the halo caused by a flaw in
Hubble's primary mirror.
(right)
The COSTAR-corrected image was taken on 10th January 1994 reveals
stellar images that are crisp and clean, and stellar magnitudes
and colors can be accurately measured. (The pre-COSTAR image was
rotated and magnified to match the scale and orientation of the
COSTAR-corrected image, and both images are 14 arcseconds on a
side).
A preliminary analysis of the data reveals the apparent presence
of white dwarf stars in the image. Prior to the Hubble
observation white dwarfs have generally been too dim to be seen
within such a cluster. A globular cluster is a tight aggregate
of thousands to millions of very old stars.
White dwarfs are the earth-sized remains of ordinary stars like
the sun. Finding them in a known globular cluster allows
accurate estimates of their age and provides clues to
reconstructing their history.
Credit: Dr. R. Jedrzejewski (STScI)
NASA, ESA