Movies of the Stars in Motion
To actually see these stars at the galactic center in motion please view this movie, which covers a period from 1992 to 2002 and shows very clearly the stars moving about a central point marked by the yellow cross—the suspected black hole. (Even more detail can be seen in this movie showing a zoomed-in view of the activity.)
After analysis of the images they were able to produce this simulation the orbits of these stars about an unseen mass. In the figure below you can see a detailed image of the orbit of the star - S2, which moves around Sagittarius A*.
Our Universe is teeming with activity—from the occasional supernova to the more mundane comet streaking through our Solar System to the mysterious dance of stars about a massive black hole at the center of the Milky Way galaxy. We live in a very dynamic cosmos only limited by what we can perceive with our senses, technology and imagination.
For more information on this fascinating place in our galaxy visit the Galactic Center Research site at the Max Planck Institute and be sure to view the slide show that is available and gives more information about this topic.
12/11/2008 Update: The ESO, the European Organisation for Astronomical Research in the Southern Hemisphere, has just released a wonderful video summarizing 16 years of observations of moving stars at the galactic center. There are some nice 3D graphics to illustrate the orbits of the stars about the massive black hole that hides at the core of the Milky Way.