The motion of the points for individual stars in the animation should be viewed as a schematic average motion. In reality, the path followed by a given star in the HR diagram can involve complex meanderings, especially if the star is massive enough to burn helium or heavier elements in the giant and supergiant phases. Any star cluster may be expected to evolve in the manner exhibited by the animation. However, only the globular clusters are old enough to exhibit the most advanced HR diagrams shown here.

To simplify the discussion, we start with a cluster in which all stars are on the main sequence by restricting attention to the more luminous part of the main sequence. In reality, for a cluster young enough that no massive stars have evolved off the main sequence, it is likely that its least massive stars are still forming and have not yet converged to the main sequence. Usage: Click "Play" to begin. Continue to click "Play" when action stops. "Step" moves forward one step and "Back" moves backwards one step. "Home" returns to the beginning from any point.