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Wolf-Rayet Nebula is a nebula which surrounds a Wolf-Rayet star. There are different types of WR-nebula, based on their formation mechanism: 1.HII regions 2.ejecta-type nebulae 3.wind-blown bubbles 4.neutral hydrogen voids and shells (may be associated gas). The nebula shown is a 'wind-blown bubbles' type.
Two artificial fish fins placed side-by-side and flapped in-phase with each another as water flows past the fins (flow direction is up). Small hydrogen bubbles (the white part of the image) allow for the wake of the fins to be visualized. The interaction of the fins creates two repeating patterns of swirling vortices known as vortex streets.