Figure 1 from Ghez's article:
The central 1.5 arcsec x 1.5 arcsec of our Galaxy.
In the background, an image of the stars taken in 2003 is displayed
and, in the foreground, colored dots show the positions of some
of these stars over almost a decade of time (multiple measurements
are taken every year, but only the annual averages are shown
here for clarity). Also plotted are the best fitting simultaneous
orbital solutions. These orbits, and a simple application of
Kepler's Laws, provide the best evidence yet for a supermassive
black hole, which has a mass of 4 million times the mass of our Sun.
Animated version of this can be found at
http://www.astro.ucla.edu/~jlu/gc/pictures/orbitsMovie.shtml. (See Article by Andrea Ghez).