MyCn18's hourglass shape is thought to have arisen from the expansion of a fast stellar wind within a slowly expanding cloud which is denser near its equator than its poles.

MyCn18之所以呈现出沙漏的外形，是因为一个缓慢扩张的云团里迅速向外冲去的恒星风造成的，其“赤道”附近的云团密度要大于两极。