This immense ball of half a million stars older than the Sun lies over 30,000
light-years away. Cataloged as M3 (and NGC 5272), it is one of about 150 globular
star clusters that roam the halo of our Milky Way Galaxy. Even in this image, individual
stars are difficult to distinguished in the densely packed core, but colors are apparent
for the bright stars on the cluster's outskirts. M3's many cool "red" giant stars take
on a yellowish cast, while hotter giants and pulsating variable stars look light blue.
A closer look at the deep telescopic view also reveals a host of background galaxies.
Itself about 200 light-years across, the giant star cluster is a relatively bright,
easy target for binoculars in the northern constellation Canes Venatici,
The Hunting Dogs, and not far from Arcturus.
[Text adapted from APOD]