What is this?

This interactive animation shows the observed and extrapolated motion of thirteen stars at the center of the Milky Way. This data was used by Andrea Ghez, M.Morris, E.E.Becklin, T.Kremenek and A.Tanner of the UCLA Galactic Center Group for the paper "The Accelerations of Stars Orbiting the Milky Way's Central Black Hole" that appeared in Nature on 21 September 2000.

One of the major achievements of the paper was in creating techniques precise enough to follow the motion of individual stars near the center of our galaxy, where the density of stars is incredibly high. Based on these observations, Ghez et al were able to confirm the existence and type of a large black hole there, at the position represented by the red-green-blue axis in this demo.

The length of each side of the box is about 0.08 parsecs. More specifically, the box length is 2 units, where each unit is an "arcsecond distance from the black hole. The center of our galaxy is about 8000 parsecs (or 8 kiloparsecs) from Earth. And at that distance, 1 arcsecond is ~0.04 parsecs = 8000 astronomical units (AU)." (Quote from an email of Jessica Lu, 8 Sep 2004.)

Who made this?

This Partiview-based Animation was made in 2004, when Jessica Lu and Andrea Ghez supplied the data to Randy Landsberg, Mark SubbaRao and Dinoj Surendran of Cosmus at the University of Chicago. Dinoj converted it to Partiview format.

For more information and downloads, see this Cosmus project page.

How do I install this?

If you're reading this (which you are), it's already installed.

How do I start this?

In Windows, click on stars.bat (or stars_geowall.bat to run it on a GeoWall, i.e. in stereo.)

In Linux, type one of


In OS X, click on stars.command

When you start it, you should see something like this. Click on the button, and move the menu out of the way.

How do I move around?


To rotate or spin, left click & hold, then move.


To stop motion, click once with the mouse.

Try pressing various buttons to see what you can turn on and off. For example, clicking on the button "g2=WHO" shows the names of the people involved in making this demo. It is turned off by default.

Documentation written by Dinoj Surendran, 31 January 2005