Drag near the center to rotate; drag near the outside to zoom

Do stars in globular clusters strongly interact with one another, or do they mostly just travel around the center of gravity unhindered? These 200 stars vary in weight by a factor of about 4. They are initially uniformly distributed inside a sphere, both in position and velocity. The trails show you the history so you can see when they interact.

I found that there is a range of speeds that makes a globular cluster. Much faster than that and the stars aren't bound together. Slower than that and they all collapse towards the center, interact strongly as they all bunch up, then some shoot away forever and others remain in the critical range of speeds. As you add more stars, the critical speed leaves the cluster sparser overall. That means that clusters with more stars have collisions (for any given star) less likely.

I've heard other people say that heavy stars tend to slow down hang out around the center of the cluster, while lighter ones get faster and often escape. Redder stars are heavier in this simulation. Blue and green dimensions were chosen at random (to make a prettier picture).

If you leave this running for awhile it looks like a painting by that famous guy who spattered paint on canvases.


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