News Release Archive:

News Release 918 of 1048

October 17, 1994 12:00 AM (EDT)

News Release Number: STScI-1994-41

Hubble Rules Out a Leading Explanation for Dark Matter


Image: Search for Red Dwarf Stars in Globular Cluster NGC 6397

Search for Red Dwarf Stars in Globular Cluster NGC 6397STScI-PRC1994-41b

Screen-use options: These files are created for viewing on your monitor



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.


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.

Object Name: NGC 6397

Image Type: Astronomical/Illustration

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


All images from this news release:

To access available information and downloadable versions of images in this news release, click on any of the images below: