This is an infrared (K-band) image of M2.  The effective band wavelength
is about 2 microns which is near the peak of the spectral energy distribution
for old, cool stars in a globular cluster.  The light from the cluster at
2 Microns is dominated by Red Giant Stars.  Since the typical ratio of
main sequence to giants stars in a globular cluster is 1 to a few hundred,
we are seeing, in this photograph, this minority population of very bright
stars.  Hence the core of the cluster is not burned out in this image.