One of the key science drivers for the extension was the study of proper motions of stars in dwarf galaxies, which requires observations taken over as long a time baseline as possible. (astronomynow.com)
In some cases, astronomers have managed to track orbital motion of the stars, which could yield more - accurate mass measurements of the stars themselves, he added. (space.com)
There is now clear evidence of relative motion of these stars around B1. (carnegiescience.edu)