A short exposure of Messier 10 in
Ophiuchus, 14,000 light years away,
provides a look into the dense core of a
modest globular cluster. Of the three presented here
(Messier 13 and
Messier 15), it is the smallest, containing about 150,000 solar
masses within a volume 50 light years across. Like all globulars, it
is old (typically 12 billion or so years) and poor in metals,
with a ratio of iron to hydrogen just 3 percent solar.
University of Illinois Prairie Observatory.