I love gravity simulations, and this video looks exactly like the simulations! It's a video of stars orbiting the black hole in the center of the milky way.
I think I remember reading somewhere that the image was taken over a period of 19 years. The orbits at the end are colored as such: (taken from the paper at
http://www.astro.ucla.edu/~ghezgroup/gc/pictures/Future_GCorbits.shtml)
Quote: "Overlaid are all known or examples of expected orbits with orbital periods less than 23 years that are expected to be detectable
in each image (14<K<16, yellow; K<17, green; K<18, cyan; K<19, magenta; K<20, tan)."
