A New Year's Gift from NASA and Penn State One of the first
targets for the Swift observatory's stellar survey was the giant
cluster Omega Centauri, which hosts millions of stars and may be
the remains of a small galaxy. Omega Centauri (also known as NGC
5139) is the largest, brightest and most massive of our galaxy's
150 or so globular star clusters. Packing some 10 million stars
into a region just 150 light-years across, Omega Centauri is
easily visible to the unaided eye despite lying nearly 16,000
light-years away. Unlike other star clusters, whose members all
have similar age and chemical makeup, Omega Centauri displays a
wide range of age and chemistry, from the ancient (12 billion
years) to the relatively recent. This presence of different
stellar populations suggests that Omega Centauri is not, in
fact, a globular cluster, but the remnant core of a dwarf galaxy
torn to shreds by the Milky Way's gravity. The false-color
ultraviolet composite from images taken through Swift UVOT's
ultraviolet filters re