Algodoo

These are particles that will explode if too many of them accrete into one object. The only way they can accrete into a count more than about 10 is if they have a spin.
This universe simulation constantly and suddenly explodes because of supernovae. Supernovae occur when 8 (number varies, depending on spin) particles coalesce. The pressure on the inside of the star, if you will, pushes internal particles close enough to cause their gravitational forces on eachother to violently slingshot eachother and everything surrounding the star outward.

Thanks.