Astronomers using NASA's Hubble Space Telescope have
determined the orbital motion of two distinct populations of stars in an
ancient globular star cluster, offering proof they formed at different times
and providing a rare look back into the Milky Way galaxy's early days.
Researchers led by Harvey Richer of the University of
British Columbia in Vancouver combined recent Hubble observations with eight
years' worth of data from the telescope's archive to determine the motions of
the stars in the globular cluster 47 Tucanae, which is located about 16,700
light-years away in the southern constellation Tucana.