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PHOTO RELEASE NO.: STScI-PRC94-41b EMBARGOED UNTIL Noon, Tuesday, November 15, 1994

SEARCH FOR RED DWARF STARS IN GLOBULAR CLUSTER NGC 6397

Left

A NASA Hubble Space Telescope image of a small region (1.4 light-years
across) in the globular star cluster NGC 6397. Simulated stars (diamonds)
have been added to this view of the same region of the cluster to illustrate
what astronomers would have expected to see if faint red dwarf stars were
abundant in the Milky Way Galaxy. The field would then contain 500
stars, according to theoretical calculations.

Right

The unmodified HST image shows far fewer stars than would be expected,
according to popular theories of star formation. HST resolves about 200
stars. The stellar density is so low that HST can literally see right through
the cluster and resolve far more distant background galaxies. From this
observation, scientists have identified the surprising cutoff point below
which nature apparently doesn't make many stars smaller that 1/5 the mass
of our Sun. These HST findings provide new insights into star formation
in our Galaxy.

Technical detail:

The globular cluster NGC 6397, one of the nearest and densest
agglomerations of stars, is located 7,200 light-years away in the southern
constellation Ara. This visible-light picture was taken on March 3, 1994
with the Wide Field Planetary Camera 2, as part the HST parallel
observing program.


Credit: F. Paresce, ST ScI & ESA
and NASA