Explanation:
Globular star cluster
Omega Centauri,
also known as NGC 5139, is 15,000 light-years away.
The cluster is
packed with about 10 million
stars much older than the Sun within a volume about 150 light-years in
diameter.
It's the largest and brightest of 200 or so known
globular clusters that roam the halo of our Milky Way galaxy.
Though most star clusters consist of stars with the same age and
composition, the enigmatic Omega Cen exhibits the presence of
different
stellar populations with a spread of ages and chemical abundances.
In fact,
Omega Cen may be
the
remnant
core of a small galaxy merging with the Milky Way.
With a
yellowish hue,
Omega Centauri's red giant stars are easy to pick out in this
sharp, color telescopic view.