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The Milky Way Galaxy is surrounded by a “halo” of “globular”
star clusters, like this one: the Great Globular Cluster in
Hercules. This cluster is about 25,000 light years distant
and about 150 light years across. In very dark skies, when
the Moon is not present, it can even be seen with the
unaided eye: a fuzzy knot about a third the diameter of the
Moon. Globular clusters are among the oldest objects in the
Universe, and made up of hundreds of thousands of very old
stars—and near the center, the stars are packed together
about 500 times more densely than in our Sun’s neighborhood
of space! The Hercules cluster is believed to be at least 12
billion years old. |
