NGC 7635 is a gas-and-dust nebula whose bubble-like shell is pushed outward by a powerful stellar wind. Hubble’s 2016 view combines four images. Its nearly round outline makes the action of a star on surrounding material unusually easy to recognize.
Trace the shell, then notice that the driving star sits away from its centre. A neat shape does not guarantee a simple explanation: ESA/Hubble notes that the star’s off-centre position raises questions. This is a nebula, not a giant soap bubble.
Source/image: NASA, ESA, Hubble Heritage Team · CC BY 4.0. Resized; colours retained.