Finding one's center, in the galactic sense

"These are the orbits of stars within the central 1.0 X 1.0 arcseconds of our galaxy. While every star in this image has been seen to move during the past nine years, estimates of orbital parameters are only possible for the seven stars that have had significant curvature detected. The annual average positions for these seven stars are plotted as colored dots, which have increasing color saturation with time. These orbits provide the best evidence yet for a supermassive black hole [at the galaxy's center], which is projected to have a mass 3.7 million times that of the Sun."

from UCLA's Galactic Center Group